How we see laser light if it travels in a straight path?
What makes some laser beams visible and other laser beams invisible?
Why is $\infty \cdot 0$ not clearly equal to $0$? I did a bit of math at school and it seems like an easy one - what am I missing?  $$n\times m = \underbrace{n+n+\cdots +n}_{m\text{ times}}$$  $$\quad n\times 0 = \underbrace{0 + 0 + \cdots+ 0}_{n\text{ times}} = 0$$  (i.e add $0$ to $0$ as many times as you like, result is $0$)  So I thought an infinite number of $0$'s cannot be anything but $0$? But someone claims different but couldn't offer a reasonable explanation why. Google results seemed a bit iffy on the subject - hopefully this question will change that. With the following circuits as examples :    and    How will the current I know how much to flow? Would any other wave travel first in the circuit and then come back and say so much current should flow? How to use hook_node_presave to change field's value Is there any difference between "offense" and "offence"? Is there a combination of "LIKE" and "IN" in SQL? Given $S \hookrightarrow T$ construct $U ≈ T$ disjoint from $S$ in Z set theory? Is it possible to print to the Report window in the Info view? Possible to save a list template and maintain lookup relationships? My issue is that I have two lists that I would like to move with their data.  While I am able to save both as templates and then upload to the new site, none of the lookup columns in my parent table are populated with data now.  Can this be done? This question led to a new package:   I would like to display the ORCID id in an author list in an IEEEtran pdf, like that:  Is there a standard way to include it in an IEEEtran article with PdfLaTeX? I used two approaches from , but I failed. One is to insert the ORCID icon in the author list. I used the blow code: \author{Ali Al-Obaidi \href{https://orcid.org/0000-0000-0000-0000}{\includegraphics[scale=1]{figures/orcid_16x16.png}}}  where orchid_16x16.png is provided in the link . But the result is that the icon is not clear enough, even I replaced it with a different size. The other approach is to use the  package, like that: \usepackage{academicons} \definecolor{orcidlogocol}{HTML}{A6CE39} \author{AAA \href{https://orcid.org/0000-0000-0000-0000}{\textcolor{orcidlogocol}{\aiOrcid}}}  However, the result is like that:  And I also got two errors: &quot;Latex Error: Encoding scheme 'TU' unknown&quot; and &quot;Bad character code (59865)&quot;. In the latest academicons.sty (see ), academicons use the font TU. However, it seems that the compiler PdfLateX cannot support this font. Thus, is there anyone that knows a standard way to include it in an IEEEtran article with PdfLaTeX? Please help me. Cycles not rendering image or movie clip used as background in the viewport First time I've used cycles rendering engine.  I'm using a movie clip as the background in short animation. Selected RBGA under Property Tab, and Transparent under Film Tab.  It looks good and individual frames in OpenGL active viewport render, and looks fine.  When I try to get it to spit out PNG files of the finished animation the objects render out fine, except no movie clip background as Blender Render engine did when using Paper Sky setting.  Operator error, or am I trying to do something Cycles won't do?  Haven't found an answer in my searches so far.  Can anyone point me in the right direction please.   Addition:  I think I found my problem after a couple more hours of research.  Post should read "operator ignorance" instead of operator error.  Too tired to try the solution tonight, everything looks better in the morning. Thanks anyway.  Sorry, I just saw your posts.  Really tired.  Much appreciation. Table column not align if give color for Table entries My code follows:  \documentclass{book} \usepackage{color,colortbl} \begin{document}  \begin{tabular}{ll&gt;{\color{red}}p{20pc}} a &amp;1 &amp;Test \end{tabular}  \end{document}   The output was:    Some unnecessary vertical space came before the last column. If I remove the tag \color{red} then everything works fine, how can I fix this?  Above said issue was fixed based on the suggestion given by David Carlisle and CarLaTeX, but the same problem was there if I use the supertabular environment, I used supertabular package for auto breaking table and the code follows:  \documentclass{book} \usepackage{color,colortbl,supertabular} \begin{document}  \begin{supertabular}{ll&gt;{\leavevmode\color{red}}p{4pc}&gt;{\leavevmode\color{black}}l&gt;{\leavevmode\color{black}}l&gt;{\leavevmode\color{red}}p{4pc}} a &amp;1 &amp;Test &amp;a &amp;1 &amp;Test\\ a &amp;1 &amp;Test &amp;a &amp;1 &amp;Test\\ \end{supertabular}  \end{document} What's the name of this flat illustration style? I want to buy some stock photos like the ones below. What is this design called?  I don't even know how to start searching... I try to download a file with wget and curl and it is rejected with a 403 error (forbidden).  I can view the file using the web browser on the same machine.  I try again with my browser's user agent, obtained by . I do this:  wget -U 'Mozilla/5.0 (X11; Linux x86_64; rv:30.0) Gecko/20100101 Firefox/30.0' http://...   and  curl -A 'Mozilla/5.0 (X11; Linux x86_64; rv:30.0) Gecko/20100101 Firefox/30.0' http://...   but it is still forbidden. What other reasons might there be for the 403, and what ways can I alter the wget and curl commands to overcome them?  (this is not about being able to get the file - I know I can just save it from my browser; it's about understanding why the command-line tools work differently)  update  Thanks to all the excellent answers given to this question. The specific problem I had encountered was that the server was checking the referrer. By adding this to the command-line I could get the file using curl and wget.  The server that checked the referrer bounced through a 302 to another location that performed no checks at all, so a curl or wget of that site worked cleanly.  If anyone is interested, this came about because I was reading  page to learn about embedded CSS and was trying to look at the site's css for an example. The actual URL I was getting trouble with was  and the curl I ended up with is  curl -L -H 'Referer: http://css-tricks.com/forums/topic/font-face-in-base64-is-cross-browser-compatible/' http://cloud.typography.com/610186/691184/css/fonts.css   and the wget is   wget --referer='http://css-tricks.com/forums/topic/font-face-in-base64-is-cross-browser-compatible/' http://cloud.typography.com/610186/691184/css/fonts.css   Very interesting. Show inline math as if it were display math (and vice versa) I'm very familiar with how symbols display differently in inline mode (with $ ... $) vs. how display math shows them (with \[ ... \] or $$ ... $$).  Two examples would be with limits  $\lim_{n\rightarrow \infty}f(x)$   vs.  \[ \lim_{n\rightarrow \infty}f(x) \]   and with sums  $\sum_{n=1}^{x} n^2$   vs.  \[ \sum_{n=1}^{x} n^2 \]   My Question is:     How do you display these things in inline mode (with all the nice inline formatting) as if they were in display mode ?   The inverse -- how to display things in display mode as if they were in inline mode -- is also of interest. Fastest Gun in the West Problem I really like the new sidebar. With the new top bar eliminating the &quot;Hot Questions&quot; area there, I think this is the perfect place for it. One-click access to time-wasting questions about topics I may or may not have an interest in. Seriously, it's a procrastinator's dream come true. The only suggestion I can add is to extend it. I assume the &quot;hot&quot; algorithm can spit out more than 12 questions, and since we now have a huge amount of room for it(without being restricted to a weird drop-down scrollbox), why not show more? If there's something else planned for that spot, disregard. At a minimum, the title could link to the , as ShaWizDowArd suggested in comments. I've been using SE for a couple years now, and I've never seen that page, so it would add visibility there.    Update: They added a link! Just noticed this, I'm pretty sure it wasn't there yesterday. When you click it, it loads 12 more. At the moment, the link disappears once clicked, so you can see a total of 24 here now. Not a link to the full list, but better: I'm developing a PHP application and I'm wondering about the best way to include multi-language support for users in other countries.  I'm proficient with PHP but have never developed anything with support for other languages.  I was thinking of putting the language into a PHP file with constants, example:  en.php could contain:  define('HZ_DB_CONN_ERR', 'There was an error connecting to the database.');   and fr.php could contain:  define('HZ_DB_CONN_ERR', 'whatever the french is for the above...');   I could then call a function and automatically have the correct language passed in.  hz_die('HZ_DB_CONN_ERR', $this);   Is this a good way of going about it?  -- morristhebear. Space between 2 paths in Illustrator How can I align 2 paths perfectly? No matter what I do I get a little space (gap between the 2 paths I create, and they are straight lines not as I saw in other questions with pixel problems)  An example:    Between every triangle is a little space, like in the example. It isn't obvious and it doesn't bother, but if I use the image (as an SVG or something) it is really obvious. default constructor for int bash chained logical operator execution order, lazy evaluation