According to electrodynamics, accelerating charged particles emit electromagnetic radiation.  I'm asking myself if the electron in an hydrogen atom emits such radiation. In , Murod Abdukhakimov says the total momentum of the electron is zero, hence it does not emit radiation. Could someone prove this statement ?  It may be an obvious question, but I can't figure out why the total momentum of the electron should always be zero, in any energy state.
I'm having trouble understanding the simple "planetary" model of the atom that I'm being taught in my basic chemistry course.   In particular,    I can't see how a negatively charged electron can stay in "orbit" around a positively charged nucleus. Even if the electron actually orbits the nucleus, wouldn't that orbit eventually decay?  I can't reconcile the rapidly moving electrons required by the planetary model with the way atoms are described as forming bonds. If electrons are zooming around in orbits, how do they suddenly "stop" to form bonds.     I understand that certain aspects of quantum mechanics  to address these problems, and that there are  of atoms. My question here is whether the planetary model itself addresses these concerns in some way (that I'm missing) and whether I'm right to be uncomfortable with it.
What is the use of the square brackets [] in sql statements? I've noticed that Visual Studio 2008 is placing square brackets around column names in sql. Do the brackets offer any advantage? When I hand code T-SQL I've never bothered with them.  Example:  Visual Studio:  SELECT [column1], [column2] etc...   My own way:  SELECT column1, column2 etc... What is Electromotive force (EMF)? How is it related to potential difference? What is  (EMF)? How is it related to the potential difference? Is it created by the potential difference in any conductor? Is it a process? Why is it called force?  Does writing EMF instead of voltage make any difference in AC circuits? (Studying alternating current I found some books using EMF while others used voltage.) Prove that if $n \in \mathbb{N}$, then $\sum_{d|n}{(d(n))^3}=(\sum_{d|n}{d(n)})^2$ where $d(n)$ is the divisor function. In the Harry Potter universe, wizards and witches have managed to keep Muggles unaware of their existence, across the planet and over many centuries. Up to the timeframe that the novels take place in (the 1990s), I can see how this can be achieved through a combination of discretion and magic, with discretion being the preferred method on occasion (e.g., you don't need magic to slip into Platform 9 3/4 unnoticed, you just need to check that nobody is looking).   Our current world of 2016, however, its a very different place. The UK is (in)famously heavily camera-monitored (). Even more poignantly, a very large (and growing) segment of the population carries an internet-enabled HD camera with them at all times and are willing to use it at a moment's notice (, but it is comedy in part because a more realistic version could happen). It looks like, the moment something magical happens in public, a video of it would be on Youtube/Facebook/Twitter and within minutes.   How does the Ministry of Magic deal with this development? Do they need to create a dedicated corps to monitor social media services and alter records as necessary? Suspend broken on Ubuntu 16.04 LTS, Dell XPS 9350 Since I upgraded from Ubuntu 15.10 to Ubuntu 16.04 LTS on my Dell XPS 9350, suspend is broken. When closing my lid the laptop will suspend, but resuming fails and it reboots. I tried pm-suspend and tried resuming, resuming failed and the laptop rebooted. I got the following errors when I got back into Ubuntu. The odd thing in my opinion is that it claims the kernel is not an official ubuntu package. Either way my Linux knowledge is not sufficient to know what's going wrong here.      EDIT: I just tried installing kernel 4.4.8 which should fix some things, but it did not fix this problem. By now I also tried 4.4.9 and 4.6 RC7. None of them fixed it for me. This is the PATH variable without sudo:  $ echo 'echo $PATH' | sh  /opt/local/ruby/bin:/usr/bin:/bin   This is the PATH variable with sudo:  $ echo 'echo $PATH' | sudo sh /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/X11R6/bin   As far as I can tell, sudo is supposed to leave PATH untouched. What's going on? How do I change this? (This is on Ubuntu 8.04).  UPDATE: as far as I can see, none of the scripts started as root change PATH in any way.  From man sudo:      To prevent command spoofing, sudo   checks ``.'' and ``'' (both denoting   current directory) last when searching   for a command in the user's PATH (if   one or both are in the PATH). Note,   however, that the actual PATH   environment variable is not modified   and is passed unchanged to the program   that sudo executes. How to change from German to English in the File Manager in Ubuntu 15.10? My months and days in my File Manager are in German, how do I change that? On the photo you see 'Dez' : It means Dezember (German for December). I also saw one day Mittwoch (German for Wednesday). How do I change that German issue? This is only my File Manager and not completly but partially. Weird. When I run followind command: qdbus I get following error:  qdbus: could not find a Qt installation of ''  I've read alot of old questions with same error but not one helps me.  I've tried execute following commands sudo apt-get install qt5-default + same for for qt4, etc. but still have same error.  If any additional information required for this issue - please add comment and I'll provide info. I've lost a command block, how can I find it? I've placed a command block making it day all the time. I want to turn it off, but I've lost it. What's the quickest way to find it? What registers to save in the ARM C calling convention? It's been a while since I last coded arm assembler and I'm a little rusty on the details. If I call a C function from arm,  I only have to worry about saving r0-r3 and lr, right?  If the C function uses any other registers, is it responsible for saving those on the stack and restoring them? In other words, the compiler would generate code to do this for C functions.   For example if I use r10 in an assembler function, I don't have to push its value on the stack, or to memory, and pop/restore it after a C call, do I?  This is for arm-eabi-gcc 4.3.0. Decode escaped Url without using HttpUtility.UrlDecode Is there any function that converts an escaped Url string to its unescaped form? System.Web.HttpUtility.UrlDecode() can do that job but I don't want to add a reference to System.Web.dll. Since my app is not a web application, I don't want to add a dependency for only using a function in an assembly.  UPDATE: Check  about the same issue. how to hide files from package explorer I asked  that turned out to have multiple correct answers. How do I pick between them to determine which to accept?  All of the answers were different. They were not the same answer given multiple times. AES plaintext is smaller than 128 bits - how to expand? We are currently developing a little AES implementation in a crypto-course at university.  As far as I know, AES uses a 128 bit block length, so all data that will be encrypted gets split up into blocks of 128 bits (16 bytes) into a 2d-array (or 1d in implementation) with 4 &times; 4 fields.  I was wondering and didn't find out what to do if the entered string to encrypt is not 128 bits long? The question is going further by thinking that there will never be exactly n &times; 128 bits of data to encrypt.  For a smaller key given by the user (e.g. "test") I know there is a key expansion algorithm defined.  But what should be done for data that is less than 128 bits? Why is it safe to use 15 A receptacles on a 20 A circuit? In a bash script, how can I redirect all standard outputs to a log file and tee the output on the screen using exec ?  log_file="$HOME/logs/install.txt-`date +'%Y-%m-%d_%H-%M-%S'`" [ -f "$log_file" ] || touch "$log_file" exec 1&gt;&gt; $log_file 2&gt;&amp;1   This code redirect all the log to the log file but not to the screen . I understand that the letter "J" is relatively new — perhaps 400–500 years old.  But since there has long been important names that begin with J, such as Jesus, Joshua, Justinian, etc., and which predate the introduction of a special letter, does that mean that the "J" sound predated the letter, or were such famous names spelled and pronounced differently? When I check for updates, I get a "Failed To Download Repository Information" error.   This is what comes up under details:   W: Failed to fetch gzip:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_natty_main_source_Sources  Hash Sum mismatch,  E: Some index files failed to download. They have been ignored, or old ones used instead. Remove empty elements from an array in Javascript Is there a term for switching syllables of words? Primary question: A common speaking mistake is to exchange syllables of words, saying "It's trace rhyme!" instead of saying "It's race time!", or pronouncing "kickin' chackatory" instead of "chicken cacciatore." Is there an existing name in poetry, linguistics, or English studies for switching syllables of (quasi-)consecutive words? I am not especially interested in the case when switching syllables results in interpretable homonyms or portmanteaus, like in the first example.  Secondary question: if not, what would you call it?  Tertiary question: is there somewhere a (playful?) taxonomy of fruitful or unfruitful lingual aberrations?