flying inside the USA
Travelling within the US as a foreign citizen without a passport
What does an unprocessed RAW file look like? Does the existence (now proved) of gravitational waves imply the existence of Gravitons? I studied the theoretical part about the Gravitational waves in General Relativity (linearization of gravity and small perturbations of the metric and so on).  But I was wondering about: since electromagnetic radiation is composed/carried by Photons (or better:the EM force), shall gravitational waves be composed/carried by Gravitons?   In the end:do gravitational waves imply the existence of gravitons? Or it's something unrelated and off topic? Is Stack Overflow merging two different accounts by email without the user's consent? I had one account through Google with email X and another account through myopenid.com. I happened to add the same email X to this myopenid.com account. My intention was to stop using the Google account in favor of the new myopenid.com account.   After some time asking and answering questions with my openid.com account I am astonished to find out that it is now merged into my Google account. That creates all kinds of privacy issues. I thought the email on my Stack Overflow account was private. Did I miss anything here?  To be clear, I wanted to preserve my privacy in the second account, but now since all my recent questions were transferred to the old account, my privacy is completely lost.  And it looks like there is no verification for the email field in my profile, so if Stack Overflow is using that info to merge, there is a very serious security bug. If it is merging based on something else, that's even worse. I think your account belongs to that user here. Let me merge it. Terrible! Why, logically, is proof by contradiction valid? Can a single molecule have a temperature? There have been several discussions regarding code-only answers (answers that contain only code blocks with no textual explanation whatsoever):         Personally, I can't see why the quality filter should let such answers through at all. The main problem I have with code-only answers, especially once they're flagged as not an answer or very low quality, is that we can't determine at a glance whether these answers are:   Genuinely attempting to answer the question  answers Trying to correct an error in the question without actually answering it Random code dumps that may or may not relate to the question even by programming language or keyword(s) in the question   In particular, what exactly is an "informative code-only answer"? Does it mean the code is self-documenting? Does it mean the code substitutes code comments for a proper write-up? This is all very fuzzy. From  to the last question above:     I have never seen a code-only answer that couldn't be made better with the addition of appropriate text. They are of lower-quality than the same answer with some text.   This text makes all the difference, IMO, between an answer and a non-answer. Without it, it's often needlessly difficult to tell.  Existing code-only answers that are good-faith attempts to answer the question should be edited or downvoted, yes. But if the quality filter already tries to block code-only questions, why not block code-only answers too? These answers are often low quality, and (almost) always have ample room for improvement, just like questions. Can I see things that I've said in chat that have been starred? I was reviewing the star on chat.SE list this morning and I noticed that quite a few of the items on the list were mine.  I was curious as to how often people enjoy the things I post there enough to star them, but I can't seem to find statistics about this anywhere.  Mana told me that no such feature exists.  (the best we could come up with is ) So here's my request - can I filter/search the chat history for things I've said that other people have starred? What is the difference between "gender" and "sex"? What is the difference between gender and sex?  says that gender is The mental analog of sex but that's too high English for me.  Basically, I'm developing a web-application that stores people's profile along with a field for gender/sex. Which name would be more appropriate?  __  [UPDATE]  After getting these good answers, I can figure out that,   Sex - Biological characteristics  Gender - Social characteristics   And, well, for my web-application, I went with the term sex, as it sounds more scientific and less political. P.S. Values for sex are clearly defined and can be easily validated (only two values * + an optional blank value).  * plus some anomalies. How to flatten a list to return a new list with all the elements? Meta sites in "Your Communities" display different reputation Does Perl have PHP-like dynamic variables? Newton's third law of motion states that every action has an equal and opposite reaction. That is the reason we do not sink into the earth, because when our weight exerts a force on the earth it also exerts an equal and opposite force on us.  But when we stand on quicksand or on fluids we can sink in. How is this possible? Does it not exert an equal and opposite force on us? Or are Newton's laws different in the case of fluids and substances of low densities? Is there any advantage to using pedal straps over clipless pedals? How does TikZ sort intersections? I used the sort by key for intersections to sort along a line, expecting the intersections to be numbered 1 through 5. Why were they numbered 4, 5, 3, 1, 2? Playing around with it, I could not seem to figure out how the order is determined. The code and image follow.  \documentclass{standalone} \usepackage{tikz} \usetikzlibrary{intersections}  \begin{document} \begin{tikzpicture}     \draw[name path=grid] [xstep=3,ystep=2] (0,0) grid (9,8);     \draw[-&gt;, name path=line] (2,1) -- (7,7);     \draw[name intersections={of=grid and line, sort by=line, name=i, total=\t}]         \foreach \s in {1,...,\t}{(i-\s) node {\s}}; \end{tikzpicture} \end{document} Accidental chown under / as root I accidentally run the following command as root chown mike -Rf / backups the point is that I added a space between / and backups my mistake, I stopped the command after 1-2 seconds, how can I recover from this? I have problems with DirectAdmin right now for example when accessing it I recive the error:  Unable to determine Usertype user.conf needs to be repaired http://help.directadmin.com/item.php?id=456   Or I stopped recieving emails, I dont even know what else is messed up right now... Why zero correlation does not necessarily imply independence How to show the solution of $\dot{x} = Ax $ is an invariant subspace? Consider the linear dynamical system $\dot{x} = Ax $ in $V$ a finite dimensional vector space.  The definition of an invariant subspace $U$ is as follows:  For all $x_0 \in U$, (initial condition), the solution $x(t)$ with initial condition $x(0)=x_0$ lies in $U$, i.e. $x(t) \in U$ for all $t \in \mathbb{R}$. Intuitively, it means if we start in a subspace we never leave that subspace.  Prove that a subspace $U \subset V$ is an invariant subspace if and only if $AU \subset U$. Increase the visibility of the association bonus by documenting it with the other privileges Feature request: Add pronouns to usercards? How to change text entry in Ubuntu 18.04 I was using Ubuntu 16.04. There it was so easy to change the text entry option. Settings > Text entry.  But when I switch to Ubuntu 18.04 I can't find such option. So how can I write in another language? How to change text entry i.e. by super+shift or something like that?