A contradiction quite possibly due to my poor understanding of time dilation
How can time dilation be symmetric?
Why is there a peeking duck in my profile pic? Cannot get specific WMS to display in Leaflet or OpenLayers 3 Strange noise when moving files When I move files, a small 'noise' noise comes through my headphones or speakers.  It only happens when moving files.  Is there a reason why moving files causes this slight static?  It only lasts for as long as the files are moving.  I'm not as much as annoyed as I am curious.  It is a Gigabyte board with a integrated sound card.  I'm running Windows 7.  I don't think it used to do this but I'm not quite sure. Can you create an illusion of empty space? I've been thinking of various ways for a crafty Illusionist/Rogue to 'hide in plain sight' by essentially creating the cover that they want to hide behind.  Ideas include things like:   Create a wall that is 2.5ft closer than it really is and hide in said space Create some innocuous barrier or container and hide within it Create a 'sheet' that essentially has what an empty room looks like 'painted' on it, so someone walking past an open door would see an empty room.   From different discussions I've had, these all should work, but the one lingering one I have is, what if my illusion is simply 'empty space'?  If I were to create an illusion of empty space and then place myself in it, would I be essentially invisible?  What if I created an illusion that was partially-empty space, like a 5x5 cube of swiss cheese? Would it seem like there was a swiss cheese cube formed around my person or could my 'fake-empty-space-image' fill the holes?  Would my 'empty space' illusion simply need to work like the aforementioned 'sheet of what I expect you to see' in order to function (and thus most likely only work from limited viewing angles)? 2D Integration With Quadratic Arg. of Delta Function Why are map tiles being repeated? Using MapServer and Openlayers I was asked to evaluate the following sum: $$\sum_{k=1}^{\infty}\frac{1}{k}\int_{\pi k}^{\infty}\frac{\sin(x)}{x}dx$$  I'm trying to use $$\int_{0}^{\infty} \frac{\sin(x)}{x}dx=\frac{\pi}{2}$$ However, it doesn't seem to work. Any help is greatly appreciated. Proof explanation $A\setminus B = A \setminus B \cap A$ $A\setminus B = A \setminus B \cap A$  Proof $A\setminus B \subseteq A \setminus B \cap A$:  $x\in A\setminus B \to x\in A \land x \notin B$  $x\in A \land (x \notin B \color{red}{\lor x\notin A})$  $x \in A \land (x\notin B \cap A)$  $x \in A\setminus B\cap A$  Proof $A \setminus B \cap A \subseteq A\setminus B$:  $x \in A \setminus B \cap A \to x\in A \land x\notin B \cap A$  $x \in A \land (x\notin B \color{red}{\lor x\notin A})$  $x \in A \land x \notin B$  $x \in A \setminus B $  Therefore $A\setminus B = A \setminus B \cap A$  I am confused how the stuff in the red is formed. Can we add an or statement to anything and ignore if its true or not if the first part of the or is true? 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. Summation of series $\sum_{n=1}^\infty \frac{n^a}{b^n}$? List of Ubuntu Versions with Corresponding Linux Kernel Version Is there a list of Ubuntu versions with default corresponding Linux kernel versions somewhere?  I would specifically like to know the most recent version of Ubuntu that still used Linux Kernel 2.x. Firefox doesn't launch in Ubuntu 13.04 Firefox starts when I use sudo in the terminal, but not from the launcher. All the other apps work like a charm, just not Firefox. How can I fix this? When a sentence uses a parenthetical plural, should the rest of the sentence treat it as singular or plural? Unexpected voltage with switch turned off Confidence interval for Bernoulli sampling I have a random sample of Bernoulli random variables $X_1 ... X_N$, where $X_i$ are i.i.d. r.v. and $P(X_i = 1) = p$, and $p$ is an unknown parameter.  Obviously, one can find an estimate for $p$: $\hat{p}:=(X_1+\dots+X_N)/N$.  My question is how can I build a confidence interval for $p$? Can the activity dropdown say more than just "+2 tag wiki"? When you earn one tag badge, and then don't click "Track the next one" in the tag badge progress tracking box for a while, and then earn a second tag badge, that box continues to show "Congratulations, you earned [the same badge as before]", rather than updating to show that you've actually earned another tag badge since then.  For instance, right now  looks like this:    Even though I  a few weeks ago and then  yesterday, my profile hasn't updated to show the new achievement.  I also didn't get the "cipher" tag badge until after the 3am watershed, even though tag badges usually appear as soon as I visit my profile after earning them (for instance, I earned the "tags" tag badge on meta.SFF.SE today the very instant I clicked on my own profile there after having become eligible for the badge). Even when I went to look at the list of my progress towards different tag badges on Puzzling, which I thought would jog the system into realising I'd actually earned the badge, "cipher" still showed up as 99/100 score even after I'd gone well past 100, until last night when the badge was finally awarded and "cipher" disappeared from my list of badges to track.  TL;DR: if I don't click "Track the next one", my tag badges update slower than they should.  It's a very unimportant bug, but there must be more people than just me who like to see the "Congratulations" thing there for a while and rest on their laurels before moving on to track their progress towards the next milestone. connectedness of uniform topology What's the fastest way to make money online? Everything in the online world is expensive, well the best things are. We all want the luxurious apartment with 10 cars garage and the best weapons but to achieve that, we need money. Which missions or activities give the most cash ? Replace unknown reference (?) with the tag from \ref or \cite While working on a document, it would be helpful if instead of a ? for unresolved references or citations the tag used in the \ref{thisthings} or \cite{Bloke1978} could appear instead.  Is there a package that turns on this behaviour?