A finite field $F$ such that $F[\sqrt{2}]$ and $F[\sqrt{3}]$ are not isomorphic (as fields)
When is $\mathbb{F}_p[x]/(x^2-2)\simeq\mathbb{F}_p[x]/(x^2-3)$ for small primes?
I'm tutoring high school students. I've always taught them that:     A charged particle moving without acceleration produces an electric as well as a magnetic field.   It produces an electric field because it's a charge particle. But when it is at rest, it doesn't produce a magnetic field. All of a sudden when it starts moving, it starts producing a magnetic field. Why? What happens to it when it starts moving? What makes it produce a magnetic field when it starts moving? Convert month name to month number in SQL Server Maybe I'm just hearing the wrong comments, but it seems that Slytherin is considered a dark house by almost everyone.  I know when both reading the books and watching the movies, I always had a feeling of foreboding when there were a number of Slytherin house members around or the time when Harry and friends went into Slytherin and felt this feeling was emphasized by the writing and film directing.  We hear very little positive about Slytherin (other than the repeated line that Harry would be a great wizard if he went in Slytherin) and there really isn't a list of great wizards who were in Slytherin House.  Even in the movie Deathly Hallows (I can't check the book - I loaned it to my sister 3 weeks after it was published and haven't seen it since!), McGonagall specifically asks Filtch to lead all the Slytherin students into the dungeon while Hogwarts is under siege by Voldemort.  She doesn't specify that any Slytherin students remain behind to help fight.  Is this intentional?  Did JKR intentionally create a bad reputation and not present any counter-examples so we'd believe all of Slytherin was bad?  Most characters in the Potter-verse are complex.  While we can admire James and Lily Potter, we also see how James teased and taunted Snape, showing us a harsh side of James, and we see that there is good in Snape.  We even see complexity in Voldemort as a villain who is mixed-blood, but hates those of mixed blood and wants purity for all witches and wizards.  With all the complex characters, it seems odd that there is essentially nothing to redeem the House of Slytherin - which is not just one character, but is a group represented by a number of characters.  But yet it seems as if it's presented, in both books and movies, as dark and full of schemers and bad people.  Are there indications, and especially more than a few or just tiny ones, that there are a fair number of good witches and wizards in Slytherin? Start script on open blender file I am wondering if we should use  or  for buttons and headings in websites and web/mobile apps? Title Case: Manage my Account Delete my Account  Sentence case: Manage my account Delete my account  In  I found the recommendation 'choose your style and be consistent'. This is it? Aren't there any other (additional) recommendations or sources. Like for specific use cases or apps where the one style would be preferred over the other? Edit: The question refers primarily to English, but differences in other languages are also good to know. Passing functions to setTimeout in a loop: always the last value? What is the difference between the command  $ env FOO=bar baz   and  $ FOO=bar baz   What effect does env have? Equidistant points across Bezier curves Retrieving Data from remote database Why would a partition be in use by the system if it isn't mounted? I've been migrating my system from btrfs to ext4 after running into performance issues with VMs. I have two hard drives in my laptop to work with. I've successfully moved my home partition, but the same steps I used aren't working for root.  Progress so far:  I've dd'd my root partition from /dev/sda3 into /dev/sdb3. I modified /etc/fstab to the following:  $ cat /etc/fstab #  # /etc/fstab: static file system information # # &lt;file system&gt; &lt;dir&gt;   &lt;type&gt;  &lt;options&gt;       &lt;dump&gt;  &lt;pass&gt; # UUID=95f13c34-96ca-49e3-bcb2-ff594df31506 /dev/sdb3               /               btrfs           rw,noatime,ssd,space_cache,discard      0 0  # UUID=0fe04f59-599f-41e2-ac30-2ad0f17a9727 /dev/sda2               /boot           ext2            rw,relatime     0 2  # UUID=44741e0f-924a-4841-80ef-2132bef84182 /dev/sda4               /home           ext4            rw,noatime,discard      0 0   and run sudo mkinitcpio -p linux. It seems to work. I'm able to boot by mounting the partition on the second disk. df shows:  $ df Filesystem      Size  Used Avail Use% Mounted on /dev/sdb3        28G   18G  9.8G  65% /   So, clearly, sdb3 is mounted, not sda3. Here's the problematic step: When I try to format sda3, which is supposedly unused, I get the following:  $ sudo mkfs.ext4 /dev/sda3 [sudo] password for stew:  mke2fs 1.42.11 (09-Jul-2014) /dev/sda3 contains a btrfs file system Proceed anyway? (y,n) y /dev/sda3 is apparently in use by the system; will not make a filesystem here!   sda3 is in use. How and why could it possibly be in use?  As per casey's comment, the output of mount:  mount | grep sd /dev/sdb3 on / type btrfs (rw,noatime,ssd,discard,space_cache) /dev/sda4 on /home type ext4 (rw,noatime,discard,data=ordered) /dev/sda2 on /boot type ext2 (rw,relatime)   As per Warwick's comment, unmounting:  $ sudo umount /dev/sda3 umount: /dev/sda3: not mounted   Mounting and umounting sda3 elsewhere works successfully, but changes nothing.  Update: More fishy behavior:  $ mount | grep sd /dev/sdb3 on / type btrfs (rw,noatime,ssd,discard,space_cache) /dev/sda4 on /home type ext4 (rw,noatime,discard,data=ordered) /dev/sda2 on /boot type ext2 (rw,relatime) $ sudo mount /dev/sda3 mnt [sudo] password for stew:  $ mount | grep sd /dev/sda3 on / type btrfs (rw,noatime,ssd,discard,space_cache) /dev/sda4 on /home type ext4 (rw,noatime,discard,data=ordered) /dev/sda2 on /boot type ext2 (rw,relatime) /dev/sda3 on /home/stew/mnt type btrfs (rw,relatime,ssd,discard,space_cache)   After mounting sda3, sdb3 is no longer mounter. Weird, huh?  As per mikeserv:  $ rmmod btrfs rmmod: ERROR: Module btrfs is in use   This is very much expected, since sdb3 is btrfs and supposed to be mounted to root. From my mkinitcpio.conf file:  MODULES="" HOOKS="base udev autodetect modconf block filesystems keyboard fsck" Does there exist a magical shell piping which would allow easily to grep through bunch of .gz log files without needing to extract them somewhere?  .gz files are Apache logs, result of log rotation. I'd like to quickly check how often certain URIs are accessed in the past. How specific does "beast you have seen" have to be for Wild Shape? Starting at 2nd level, you can use your action to magically assume the   shape of a beast that you have seen before.   This doesn't say anything about the gender or age of the beast, so can a druid change into a female bear if he has only seen male bears? Can he change into a bear cub if he has only seen adult bears? What about hens/roosters/chickens, which look quite a bit different? Or does the gender of the animal shape just match the gender of druid? I think we can all agree, this sucks:  If you've been around a little while, you've probably encountered hundreds of answers like this in various forums, some of them even marked as &quot;The Answer&quot; by well-meaning1 forum admins looking to close a thread. We could try to enumerate the commonly-observed problems with it...  Link is probably broken If link isn't broken, it's spam If link isn't spam, it's to some broadly-related resource that the answerer found by pressing &quot;I'm feeling lucky&quot; when googling the question's title.  ...but the real issue here is that we don't know! Even if the link was originally pointing directly to the most awesomeest answer ever for exactly the question being asked, there's nothing in the answer itself to even hint at what direction we're being pointed in. Strip the markup, and this is what you're left with:  i think you should take The tutorial HERE! This will help you a lot  Is there even one tiny speck of information there? No. Even the title of the page being linked to would have provided something to go on, but that was entirely too much work. So let me be clear: this sort of response is not an answer. If you see this, flag it. Moderators, if you see it flagged, delete it. There's really only one valid exception to this rule, and that's when the question is:  Suggest me some tutorials where i can learn quick.  Don't get me wrong, it's still a bad answer - but when the question is kinda asking for bad answers this is to be expected. Close or flag the question and move on - this is much more efficient than hanging around to babysit it by deleting every crap answer that inevitably shows up. If you're still reading, you're probably getting really bored by now. &quot;Gee, Shog - answers that contain ZERO information are terrible, horrible, very-bad things? What shocking revelations will you share next?&quot; Yeah. It's really simple... Except, . See, the problem is that once you step away from black-and-white &quot;answers / doesn't answer&quot; decision-making, things get... Interesting. And all those other answers with links in them See, this is an answer:  And so is this:  Yes, they're both very short, and yes, they contain links. But strip the markup, and you still get at least a little bit of useful information. Does that mean these answers should forever hang around the site? No, not necessarily - if it turns out they're just not that useful, they should probably still be removed - or at very least, down-voted so that they rank below other answers. Just remember: if the text of the post contains an honest attempt at answering the question, then it is an answer - so don't flag it otherwise, and if you do, don't complain if your flag gets declined. Answers &amp; Apples If you're still confused, forget about answers. Think about apples instead:  Answers are just like that, but less tasty in pies.  1 By which I mean to say, &quot;criminally lazy&quot; What is the equivalent of Windows System Properties or Device Manager? I am new to Ubuntu. In Windows, if I want to know my system properties/configuration, I can see it by going to Control Panel and clicking on the System icon. I can also get a detailed list of the hardware detected/installed by going to the Device Manager.  What are the equivalents of these features in Ubuntu, where a user can see his or her system properties and hardware configuration, like RAM, CPU/processor, hard disk capacity, etc.?    Example of Windows System Properties: Adding newmode with Xrandr - "800x480_60.00" I have 5-inch a 800x480 tft connected to the LVDS connector on a Portwell WADE-8020 mini-ITX embedded system board. I would like to build a XMBC/Kodi box for streming my music from my freenas PC with the tft showing what is been played, I got as fare as this...   sudo xrandr --newmode "800x480_60.00"  29.50  800 824 896 992  480 483 493 500 -hsync +vsync`enter code here   then,  sudo xrandr --addmode LVDS1 800x480_60.00   now that I get the correct resolution, I now have a black band on the top of the screen.  sudo xrandr --output LVDS1 --set "scaling mode"  "Full aspect"   However this did not solve the issue, also I know I need to amend the /bin/sh file with this from googling so I don't need to keep doing this at every boot. But I don't know how to as I'm very new to Linux.  #!/bin/sh xrandr --newmode "800x480_60.00"  29.50  800 824 896 992  480 483 493 500 -hsync +vsync xrandr --addmode LVDS1 800x480_60.00 If I use the starting wealth rolls of my class, do I keep any remaining money left over? If I use the starting wealth rolls of my class, do I keep any remaining money left over after I buy equipment?  In D&amp;D 5e you can roll the 4d4 &times; 10 to determine starting gold, forgoing any equipment your class and background  gets.  This is not up for question.  What is up for question is whether or not the PC keeps any remaining gold that they don't spend on equipment.   As far as I have been able to tell, this is not explicitly stated in the PHB nor in the Basic Rules documents. How can I successfully finish a hobby game project in my free time?  How do I motivate myself to keep it up and drive right through to the finish without losing interest or motivation along the way? Which databases use real multidimensional indices? Is oracle ever using several indices to get data from tables, or will it always take the one that seems to have the highest selectivity? How about other dbms? Why can I only change my Stack Overflow name once every 30 days? I have a  on Stack Overflow. I recently decided to change the name on my profile. I did this, but I made a spelling mistake! I wrote "Kryton" instead of "Kryten"! When I tried to fix this, a message came back saying that I can only change my profile name every 30 days. Why? Is there any way I can fix my profile name? Finding the id of a parent div using Jquery