Can a mass-less charged particle exist?
Massless charged particles
Is there a word that describes a parent whose child has died?   Along the lines of "orphan", "widow", and "widower", is there a single word for a parent who has lost a child (of any age)? Is there any difference in meaning between 'efficacy' and 'efficiency'? Proving the two given vectors are orthogonal How to edit / how to format box overlapping with footer when scrolling down I just edited an answer on Unix&amp;Linux and when scrolling down, the semi-transparent right sidebar boxes "How to edit" and "How to format" kept their fixed positioning and overlapped with the page footer.     While posting this, I have seen several (not) duplicate questions about this issue, and although from my personal taste, I would prefer the boxes to stop scrolling before the footer is reached, I can accept the development teams decision to let it overlap.   However, on all those other posts, the boxes had an opaque background, so that the footer was hidden and the box content was readable. Here the boxes are transparent though, so the texts get mixed and are no longer well readable. How to force Windows to rename a file with a special character? I have a song that Windows can't play because there is a question mark in the name of the file.  "Where Have All the Cowboys Gone?.ogg" // as an example   So I try to rename it and Windows complains whether I try it in Explorer or from command prompt.  Error I get when trying to copy, rename, or move is:     The Filename, directory name, or volume label syntax is incorrect   Is there a Windows way to force a rename in this case?   Update  I'll keep an eye on this question, but after 13 answers and many attempts (aside form 3rd party solutions) it seems that Windows can't do this (or at least my windows can't, no short names). So I'm accepting the answer which was my original solution anyway of using Linux. It would be nice to see Windows handle this somehow, so don't stop just because I've accepted this answer, the question still stands! Why is $\mathbb{R}^2$ not a subspace of $\mathbb{R}^3$? Change rep required to downvote on MSE Adding tags to files in OS X: How to use, where are tags stored, and will they work on a network? Can I use a Thunderbolt display for a macbook pro with a mini display port? C++ catching all exceptions Is there a c++ equivalent of Java's  try {     ... } catch (Throwable t) {     ... }   I am trying to debug Java/jni code that calls native windows functions and the virtual machine keeps crashing.  The native code appears fine in unit testing and only seems to crash when called through jni.  A generic exception catching mechanism would prove extremely useful. PGFplots foreach equivalent to TikZ's with multiple variables separated by a slash If $e^{itx_n}$ converges for every $t\in\mathbb R$, then does $x_n$ converge? If A and B play a game with a fair coin such that A wins by getting consecutive TT for the first time, while B wins by getting a consecutive TH.  Who has higher probability of winning the game?   I tried the following method but not sure:  For A to win,     TT, HTT, HHTT ... that is, 2-k for each game length k   For B to win,     TH, HTH, HHTH ... that is, 2-k for each game length k   So ultimately I am getting same probability of each to win. How does delete[] know it's an array? What if my State / Country doesn't have a Ubuntu LoCo Team? How can I start one? I know what an Ubuntu Team is and , but what can users do if their area doesn't have a LoCo team? What is the name of this connector from a fan? I am EE hobbyist and I often used recycled parts in my projects. I came across this connector to a Heat Sink Fan and would like to know the name of it.  Thanks for the help. At what time will the upcoming Ubuntu release be made available? Every six months a new Ubuntu version will be released. Does anyone know at which time this will be? Should black holes be considered two-dimensional or three-dimensional? I need to calculate no of possible substrings containing "00" as a substring. I know the length of the binary string.  Eg: for a string of length 4, possible substrings are: 0000 0001 0010 0011 0100 1000 1001 1100  I just need the number of possible combinations, not enumerate all of them. Bash Brace Expansion & Variables I have a find command:  find Directory/{Alpha,Bravo,Charlie} arg1 arg2   I want to replace Alpha,Bravo,Charlie with $find_dir  find Directory/{$find_dir} arg1 arg2   however the latter expands to   find Directory/{Alpha,Bravo,Charlie} arg1 arg2   rather then   find Directory/Alpha Directory/Bravo Directory/Charlie arg1 arg2   Why? It's part of a fairly complex bash script that may have more or less directories, not all which are relevant (so globbing Upload/* would not work). So if I setup three now and add another, I'll have to manually add it in later. Plus I need it run from the root of directories to keep finds outputs perspective (./Upload/Dir/file as opposed to ./Dir/file).   But using a variable would permit me to change that as needed and keep it relevant to other parts of the script.