Time dilation in satellites
Why does GPS depend on relativity?
Changing the value of an element in a list of structs I have a list of structs and I want to change one element. For example :  MyList.Add(new MyStruct("john"); MyList.Add(new MyStruct("peter");   Now I want to change one element:  MyList[1].Name = "bob"   However, whenever I try and do this I get the following error:     Cannot modify the return value of   System.Collections.Generic.List.this[int]‘ because it is not   a variable   If I use a list of classes, the problem doesn't occur.  I guess the answer has to do with structs being a value type.  So, if I have a list of structs should I treat them as read-only? If I need to change elements in a list then I should use classes and not structs? Why cannot this question with an open bounty be closed? Update Migration Path List for Non-Moderators I have got codes like the following (generated by Kile). How can I add a caption. I guess I should have used the table environment. Is there any solution now?  \newcommand{\mc}[3]{\multicolumn{#1}{#2}{#3}} \begin{center} \begin{tabular}{rccll}      &amp;   &amp; \mc{3}{c}{Colin}\\      &amp;   &amp; a &amp; \mc{1}{c}{b} &amp; \mc{1}{c}{c}\\\cline{3-5} Rose &amp; \mc{1}{c|}{A} &amp; \mc{1}{c|}{(1,2)} &amp; \mc{1}{c|}{(2,5)} &amp; \mc{1}{c|}{(4,4)}\\\cline{3-5}      &amp; \mc{1}{c|}{B} &amp; \mc{1}{c|}{(7,4)} &amp; \mc{1}{c|}{(3,5)} &amp; \mc{1}{c|}{(0,6)}\\\cline{3-5} \end{tabular} \end{center} Prove that given $A\subseteq\mathbb{R}$, if has a maximum $a_0$, then $a_0$ must be the supremum.   In order to prove this, I have written the following:  Let $A\subseteq \mathbb{R}$, nonempty set because $a_{0}$ $\in A$ for hypotesis. Then, since $a_{0}$ $\in A$ is the largest element of the set $A$   (i.e. for each element $A$ of A we have that $ a\leq a_{0}$) $A$ is bounded above. Then, A has a supremum. Let $s$ be the least upper bound of $A,$ so we have that for each element $a$ of $A$, $a\leq s$, for being $s$ an upper bound. In particular, $a_0\leq s$, which implies that $s=a_0$.   Then, we have that $\sup(A)=\max(A)=a_0$, which is exactly what we wanted to prove.  Observation: this proof is true if $s \in A$   I'm not sure if my proof is correct. I will be thankful if someone tells me. When creating presentations in , those little symbols that you can click on and will take you to different parts of your presentation are automatically included on your slides.  I don't like that, but decided not to try and change it for now. The problem is that when I gave my presentation to my supervisor to revise, the first thing he did was cross the symbols out in red, meaning: take this out!  What should I do? Is there an easy command to get rid of those symbols or do I have to change the theme of my presentation to get rid of the symbols? How to create wifi hotspot in Ubuntu 17.10 Why does 'g' sometimes read as 'j'? Most words with 'g' read as 'g'   Geek Goose Goods Goal   But sometimes 'g' reads as 'j'   Gymnastics Genesis Genius Genetic   And in the middle of a sentence, compare:   Log Logistics   Or   Frag Fragile Any $B \subset \{10,11,...,99\}$, with $|B| =10$ has two subsets such that $\sum_{a \in B_1} a = \sum_{b \in B_2} b$ Let there be $B \subset \{10,11,...,99\}$, with $|B| =10$. I need to prove, using the pigeonhole principle, that there are at least two disjoint subsets of $B$ (and none empty) where the sums of their elements are identical. I.e. $\exists B_1 \ne \varnothing, B_2 \ne \varnothing$ such that $B_1 \bigcup B_2 = B$, $B_1 \bigcap B_2 =\varnothing$ and $$\sum_{a \in B_1} a = \sum_{b \in B_2} b$$ Draw Vertices of Regular Polygon I am trying to draw just the nodes (no sides) at the vertices of a regular hexagon.  should be easily modified to accomplish what I want, but I am such a novice that I have difficulty understanding the example. Ideally, each vertex would be a separate named node so that I can easily draw edges between them (I will be making several different graphs using these same nodes). iPhone 7 Plus takes days to turn on showing Apple logo or black screen I’ve had this issue for months but in the last couple of days it’s got very very bad.  When my phone runs out of battery it needs like 2–3 days to turn back on. At the beginning of this problem the phone would need about 1h. Every time when my phone goes off again the time to switching on goes up.  What does this all look like? Well, when my phone died I put it on the charger, then the logo appears and goes off. When it goes off, a black screen pops out with a little white line on in it, then it turns on back to Apple logo. It keeps doing this until it turns on which is 1 or 2 even now 3 days.  I tried to restore it and also update it but nothing happens, literally nothing happened. Mach-O 64-bit format does not support 32-bit absolute addresses. NASM Accessing Array Bootstrap CSS Active Navigation How do I debug when the system freezes or when it crashes back to login? I am fairly new to Ubuntu and I was wonder what a good way is to debug when something crashes?   For example: I installed 11.04 and the default media player banshee makes my laptop crash after a few minutes of playing music. Since the system completely freezes and there is not error message it's hard to find out what is wrong.  Second problem I have is that sometimes the system crashes to login. I am suspecting it to be a Chromium or Flash but I am not 100% sure.  So anybody got some tips on how to debug stuff like this? I was trying to give the wording "isomorphic groups have the same structure" a precise interpretation, at least for the finite order case. A positive answer to my final question would reach the goal, as it would translate a "$\cong$" between groups into a "$=$" between sets.    For $n$ positive integer, let be:   $I_n:=\{1,\dots,n\}$; $G$, $\overline G$ groups of order $n$; $\psi\colon G \rightarrow \overline G$ isomorphism; $f$, $\bar f$ bijections; $\theta$, $\bar \theta$ embeddings; in general, $\varphi^{(\alpha)}$ the isomorphism between symmetric groups on sets of the same cardinality, defined by $\sigma \mapsto (g \mapsto (\alpha\sigma\alpha^{-1})(g))$, where $\alpha$ is a bijection between the sets; $S_n$ the symmetric group of degree $n$.   Visually:  $$ \newcommand{\ra}[1]{\kern-1.5ex\xrightarrow{\ \ #1\ \ }\phantom{}\kern-1.5ex} \newcommand{\ras}[1]{\kern-1.5ex\xrightarrow{\ \ \smash{#1}\ \ }\phantom{}\kern-1.5ex} \newcommand{\da}[1]{\bigg\downarrow\raise.5ex\rlap{\scriptstyle#1}} \begin{array}{c}    I_n     &amp;   &amp;    I_n      \\     \da{f}         &amp;           &amp;     \da{\bar f}          \\    G &amp; \ras{\psi} &amp;    \overline G  \\     \da{\theta}         &amp;           &amp;     \da{\bar \theta}          \\    \operatorname{Sym}(G) &amp; \ras{\varphi^{(\psi)}} &amp;    \operatorname{Sym}(\overline G)  \\     \da{\varphi^{(f)}}         &amp;           &amp;     \da{\varphi^{(\bar f)}}          \\    S_n &amp;  &amp;    S_n  \\ \end{array} $$     Is it $(\varphi^{(f)}\circ\theta)(G)=(\varphi^{(\bar f)}\circ\bar \theta)(\overline G)$? "For security reasons, framing is not allowed; click OK to remove the frames." on Imgur upload Ok first, there's that lugubrious use of the semicolon; not necessary.  Second, I didn't open a frame!  You did!  Alls I tried to do is upload a 5MB animated .gif file via Imgur.    Looking further into this, Imgur actually posts an error when you upload an animated .gif larger than 2MB.    Go figure! Remember all opened files with split windows and their positions in Emacs Why do professional print houses use gamut-limiting CMYK? I recently had some business cards printed, and was warned to use the CMYK colour space if providing TIF files.  When I tried saving from Paint Shop Pro to a CMYK, of course the colours came out very much duller, so I provided a different file type that preserved my colours using RGB. To my horror, the cards came back nevertheless converted to the CMYK dull shades.    A few months previously I had been in a hurry and had printed my own one-sided quasi business cards using glossy photo paper and a cheap home printer.  This reproduced my desired colours perfectly.  Since the whole point of using professional printers is quality (though I admit bulk as well), why do they not use printers that can cope with the RGB colour range?   FYI: the main colour in question, which I chose very carefully, is a slightly yellow-tinged lawn green, which I understand doesn't feature in the CMYK gamut.  So why use that gamut, and is there anything I can do to overcome this issue and get cards printed in the colour I have chosen? ESM is available for 12.04, which enables Advantage customers to keep receiving kernel updates and updates for many user space packages. In our case it's very important to know if we'll be able tot use Ubuntu 14.04 safely after April '19, because it is not possible to upgrade our application and migrate it to say, 16.04. The new hot questions algorithm sometimes recurses The hot questions algorithm . I like the effects, since I see lots of new interesting stuff every day rather than waiting 6-8 weeks varying amounts of time for the list to update.  However, the new algorithm also has the interesting side effect of recursing the same question:    Of course, this is a world-shattering workflow-breaking unicorn-hating waffle-despising ERROR tremendously minor matter. But, if the SE devs have opportunity during their amazingly large amounts of free time, it might be nice to add a check for the current page before populating the hot questions list.