Why didn't Thanos go after the orb personally? In Guardians of the Galaxy, if Thanos knew the orb contained an Infinity Stone (one of the most powerful artefacts in the galaxy), why did he send Ronan to retrieve it?  It was pretty clear from their short exchanges that Thanos and Ronan pretty much hated each other. Why would Thanos trust Ronan with such a hugely important task?  I know initially, Ronan didn't know that the orb contained an infinity stone, but Thanos was still taking a pretty big risk sending him to retrieve it.   Even with two of Thanos' daughters on board Ronan's ship, the orb would ultimately pass through Ronan's hands before it reached Thanos, so there was always the possibility he would discover it's contents.  Is there any reason established as to why Thanos doesn't go after the infinity stone personally?
Why didn't Thanos come to Earth to retrieve Tesseract by himself? In the Avengers movie, why didn't Thanos personally come to Earth instead of Loki? Or, if Loki's skills were required, why didn't he come with Chitauri? He knew that humans were primitive; there wouldn't be any threat and he could personally secure Tesseract.  AFAIK, the movie didn't display much. Is there any other source answering this?
How can I install Ubuntu on a second hard drive with Windows being on the first? I have recently got an Alienware M17x R4 and since it has two hard drive bays I was thinking of putting my hard drive from my old laptop and installing Ubuntu on it without making any changes to the drive that has Windows on it. Also if possible to add a entry to the Windows boot loader to boot Ubuntu instead of using GRUB. Deriving the conditional distributions of a multivariate normal distribution We have a multivariate normal vector ${\boldsymbol Y} \sim \mathcal{N}(\boldsymbol\mu, \Sigma)$. Consider partitioning $\boldsymbol\mu$ and ${\boldsymbol Y}$ into  $$\boldsymbol\mu = \begin{bmatrix}  \boldsymbol\mu_1 \\  \boldsymbol\mu_2 \end{bmatrix} $$ $${\boldsymbol Y}=\begin{bmatrix}{\boldsymbol y}_1 \\  {\boldsymbol y}_2 \end{bmatrix}$$  with a similar partition of $\Sigma$ into $$  \begin{bmatrix} \Sigma_{11} &amp; \Sigma_{12}\\ \Sigma_{21} &amp; \Sigma_{22} \end{bmatrix} $$ Then, $({\boldsymbol y}_1|{\boldsymbol y}_2={\boldsymbol a})$, the conditional distribution of the first partition given the second, is  $\mathcal{N}(\overline{\boldsymbol\mu},\overline{\Sigma})$, with mean $$ \overline{\boldsymbol\mu}=\boldsymbol\mu_1+\Sigma_{12}{\Sigma_{22}}^{-1}({\boldsymbol a}-\boldsymbol\mu_2) $$ and covariance matrix $$ \overline{\Sigma}=\Sigma_{11}-\Sigma_{12}{\Sigma_{22}}^{-1}\Sigma_{21}$$  Actually these results are provided in Wikipedia too, but I have no idea how the $\overline{\boldsymbol\mu}$ and $\overline{\Sigma}$ is derived. These results are crucial, since they are important statistical formula for deriving Kalman filters. Would anyone provide me a derivation steps of deriving $\overline{\boldsymbol\mu}$ and $\overline{\Sigma}$ ? Thank you very much! FileSystemWatcher Changed event is raised twice Transformation of Random Variable $Y = X^2$ I'm learning probability, specifically transformations of random variables, and need help to understand the solution to the following exercise:      Consider the continuous random variable $X$ with probability density function $$f(x) = \begin{cases} \frac{1}{3}x^2 \quad  -1 \leq x \leq 2, \\ 0 \quad \quad \text{elsewhere}. \end{cases}$$ Find the cumulative distribution function of the random variable $Y = X^2$.   The author gives the following solution:   For $0 \leq y \leq 1: F_Y(y) = P(Y \leq y) = P(X^2 \leq y) \stackrel{?}{=} P(-\sqrt y \leq X \leq \sqrt y) = \int_{-\sqrt y}^{\sqrt y}\frac{1}{3}x^2\, dx = \frac{2}{9}y\sqrt y.$  For $1 \leq y \leq 4: F_Y(y) = P(Y \leq y) = P(X^2 \leq y) \stackrel{?}{=} P(-1 \leq X \leq \sqrt y) = \int_{-1}^{\sqrt y}\frac{1}{3}x^2\, dx = \frac{1}{9} + \frac{1}{9}y\sqrt y.$  For $y &gt; 4: F_{Y}(y) = 1.$    Previous to this exercise, I've managed to follow the solutions of two similar (obviously simpler) problems for a strictly increasing and strictly decreasing function of $X$, respectively. However in this problem, I don't understand the computations being done, specifically:    How does the three intervals $0 \leq y \leq 1$, $1 \leq y \leq 4$ and $y &gt; 4$ are determined? In the two previous problems I've encountered, we only considered one interval which was identical to the interval where $f(x)$ was non-zero. In the case where $0 \leq y \leq 1$, why does $P(X^2 \leq y) = P(-\sqrt y \leq X \leq \sqrt y)$ and not $P(X \leq \sqrt y)$? I have put question marks above the equalities that I don't understand.   I think I have not understand the theory well enough. I'm looking for an answer that will make me understand the solution to this problem and possibly make the theory clearer. I understand the idea of a focal length for a single lens, i e the distance from the lens to the point at which parallel rays of light converge. However, in the case of a photographic lens with multiple lens elements, where exactly is the focal length of the lens as a whole measured from? Why mass terms are forbidden? I would like to clarify my understanding on why mass terms in Lagrangians of gauge theories are forbidden.  It's often repeated that particle masses are forbidden by electroweak symmetry because it is a chiral theory. I want to make a distinction between fermionic masses and gauge boson masses.   Looking through the transformations of gauge boson mass terms, it seems that these are in fact always forbidden by their respective gauge symmetry. Is this correct? (So if there was no SU(2) symmetry, the photon and gluon would still need to be massless?)  In which case, the electroweak symmetry is actually responsible for forbidding all other mass terms (i.e. weak boson masses and fermion masses) due to the usual chiral arguments. Is this correct? LaTeX figures side by side I want to place 2 images side by side in LaTeX. I have 2 .png files and I don't understand how to do it in LaTeX. I have tried many ways but could not get a good result. EDIT: Summary  I think I've found the best definition of what I want thanks to the discussion with @M. Tibbits:  When I open or refresh the SO, I get a notification of new activities that are of interest to me. Today these are (hard-coded): answers to my questions and comments addressed to me. I want a bit more control over it, that's all.     Yes, I've read  and , but I think I add new (good :) ) reasons for re-asking it:  The first question was answered before this so handy "inbox" notification feature was implemented. So now using favorites for "watching" a question is wrong, IMHO, for 2 reasons:   it splits essentially the same functionality (of getting notified when there is an activity you are interested in) between 2 very different user interfaces it's cumbersome - I need to: 1) add question to favorites; 2) click on my profile dropdown; 3) click on the "favorites" line; 4) see all my favorites with recent activity; 5) select the one I watch; 6) repeat this process occasionally to get updates; and 7) possibly remove the question from favorites at the end. All this as opposed to this little red button when there are news.   Favorites are different in nature that watching. I add a question to Favorites when I find the answers useful to me in my work, so I may want to have it handy in the future. By watching an interesting question I will be able to decide whether I want it in faviorites, after I see the answers.  EDIT: I see that I was not clear enough.  I want to add a question to Favorites when:   it has some good answers the question and answers are relevant in my work I want to keep them handy as my long-term (persistent) knowledge base   I want to watch a question for short while (matter of days/weeks) when:   it is interesting / relevant I want to follow it to see what are the answers. Then I can decide whether I want it in my favorites   As you see, the main differentiators are good answers and long/short term. For short-term, automatic notification is better.  Bottom line, all I ask is "watch this question" checkbox (which may expire after say a week if there is a need to free resources) In Ruby on Rails, how do I format a date with the "th" suffix, as in, "Sun Oct 5th"? Can't update because the word prox* is blocked I live in Ethiopia and the government blocks all urls with the word "proxy" in them. I couldn't use that word in the title above because that would make the url contain the word proxy.   When I apt-get upgrade I get errors because some packages like libproxy1, libproxy1-plugin-gsettings, libproxy1-plugin-networkmanager, python-libproxy all contain the p word.  Therefore, it is all blocked. I tried putting the urls into proxy sites, but they all just returned to their home page.   Are there any other solutions? Storing C++ template function definitions in a .CPP file I have some template code that I would prefer to have stored in a CPP file instead of inline in the header.  I know this can be done as long as you know which template types will be used.  For example:  .h file  class foo { public:     template &lt;typename T&gt;     void do(const T&amp; t); };   .cpp file  template &lt;typename T&gt; void foo::do(const T&amp; t) {     // Do something with t }  template void foo::do&lt;int&gt;(const int&amp;); template void foo::do&lt;std::string&gt;(const std::string&amp;);   Note the last two lines - the foo::do template function is only used with ints and std::strings, so those definitions mean the app will link.  My question is - is this a nasty hack or will this work with other compilers/linkers? I am only using this code with VS2008 at the moment but will be wanting to port to other environments. Can I downgrade to Mavericks after installing Yosemite (beta/developer preview)? I have installed the developer preview for Yosemite.  Huge mistake. Everything in my workspace is broken.  I don't have any sort of backup image. I was wondering if I could re-download Mavericks and run the installer - would that effectively downgrade me back to Mavericks? Customizing titlesec-etoc (further question) Rectangle with cross on title bar I have installed Ubuntu 14.04 and I think that I have found a bug. When I open terminal and  go to edit profile preferences I get a rectangle with a cross on the title bar. It happened with other applications too. Here are the screen shots: How to use Cubic to create a custom Ubuntu live CD image? Is there a robust command line tool for processing csv files? How to convert an MKV to AVI with minimal loss To convert an MKV to AVI, I do two things. The first thing I do is this:  ffmpeg -i filename.mkv -vcodec copy -acodec copy output.avi   or this:  ffmpeg -i filename.mkv -sameq -acodec copy output.avi   Either of these will convert the MKV to an AVI, but the problem is that the video does not play smoothly for some reason. That's fine though, because if I do one more thing it gets fixed:  ffmpeg -i output.avi -vcodec mpeg4 -b 4000k -acodec mp2 -ab 320k converted.avi   After I do this then the file plays without problem. I had success doing it this way for one file, but then I tried it on another file, and there is a slight, but noticeable loss in video quality. This is the output I get when doing the second step:  FFmpeg version 0.6.1, Copyright (c) 2000-2010 the FFmpeg developers   built on Dec 29 2010 18:02:10 with gcc 4.2.1 (Apple Inc. build 5664)   configuration:    libavutil     50.15. 1 / 50.15. 1   libavcodec    52.72. 2 / 52.72. 2   libavformat   52.64. 2 / 52.64. 2   libavdevice   52. 2. 0 / 52. 2. 0   libswscale     0.11. 0 /  0.11. 0  Seems stream 0 codec frame rate differs from container frame rate: 359.00 (359/1) -&gt; 29.92 (359/12) Input #0, avi, from 'output.avi':   Metadata:     ISFT            : Lavf52.64.2   Duration: 00:04:17.21, start: 0.000000, bitrate: 3074 kb/s     Stream #0.0: Video: mpeg4, yuv420p, 704x480 [PAR 229:189 DAR 5038:2835], 29.92 fps, 29.92 tbr, 29.92 tbn, 359 tbc     Stream #0.1: Audio: vorbis, 48000 Hz, stereo, s16 Output #0, avi, to 'converted.avi':   Metadata:     ISFT            : Lavf52.64.2     Stream #0.0: Video: mpeg4, yuv420p, 704x480 [PAR 229:189 DAR 5038:2835], q=2-31, 4000 kb/s, 29.92 tbn, 29.92 tbc     Stream #0.1: Audio: mp2, 48000 Hz, stereo, s16, 320 kb/s Stream mapping:   Stream #0.0 -&gt; #0.0   Stream #0.1 -&gt; #0.1   I just used arbitrarily large settings on the second step and it worked nicely before but not in this case. What settings should I use? Is there a drupal.org API for retrieving the list of available modules, a description of them and available versions? Separate selected UV map vertices from surrounding vertices How do I break the selected UV map from its surrounding vertices? Centering figure captions in IEEEtran I am working on a paper using the IEEEtran template in LyX.  I have run into a problem: While the contents (in this case, a table) of the figure float are centered, the caption is aligned to the left (see screenshot below). How can I center the caption as well?    This is generated by the following LyX document:    What I've tried:   Center the table (the table is centered) Center all the contents in the float (only the table is centered) Select the caption and center it (no effect)   Technical details:   LyX 2.0.5.1 Mac OS X 10.7.5 (Lion) All centering was performed by Right Click>Paragraph Settings>Align: Center