As a kid, I was taught that that blue and yellow make green, yellow and red make orange, and red and blue make purple - forming the subtractive color wheel. As an adolescent I was taught that blue and green make cyan, green and red make yellow, and red and blue make magenta - forming the additive color wheel. Somewhere in that time I was also taught that the colors of the rainbow are ROY G. BIV.  That last one is the only one that makes much sense to me in physics because perceivable light is not somehow a cycle, but rather a tiny segment of the EM spectrum.  Why do the colors at the top and bottom of the spectrum seem to be mixable? Is there anything in nature that indicates this should be the case? Is this just a psychological or physiological phenomenon?
When people are asked to match monchromatic violet light with an additive mix of basic colours, they (paradoxically) mix in red.  In fact, the CIE 1931 color space chromaticity diagram shows this effect begins at about 510nm (greenish-cyan), where people mix in no red.  From that point on, the higher the frequency of the light source, the more red they mix in.    This effect is reflected by the red curve of the , which has an additional bump in the area of blue light.  However, that curve does not match the actual spectral sensitivity of red cones.  So where does this additional perception of red at higher frequencies come from?
Convert integer to hexadecimal and back again new array.sty and colortbl.sty incompatibility? I just upgraded my texlive distribution and can no longer insert space in table rows using \\[x pt] syntax when colortbl is loaded.  It seems that recent changes to array.sty might be the problem as this is the only package to change recently.  Can anyone suggest a workaround?  MWE  \listfiles \documentclass{article} \usepackage{colortbl} \begin{document} \begin{tabular}{l}   \hline   No space below with \texttt{colortbl.sty} loaded. \\[10mm]   \hline \end{tabular} \end{document}   File versions in use:   article.cls    2014/09/29 v1.4h Standard LaTeX document class   size10.clo    2014/09/29 v1.4h Standard LaTeX file (size option) colortbl.sty    2012/02/13 v1.0a Color table columns (DPC)    array.sty    2018/04/07 v2.4g Tabular extension package (FMi)    color.sty    2016/07/10 v1.1e Standard LaTeX Color (DPC)    color.cfg    2016/01/02 v1.6 sample color configuration   pdftex.def    2018/01/08 v1.0l Graphics/color driver for pdftex The Stack Exchange beta iOS app distributed over TestFlight will expire in 2 days has expired. After the 100 day test period, the app won't start any more so all beta testers can't use the app then.  Can we please get an updated release so we don't have to remove the app and install the current release from the App Store instead? Explain why $E(X) = \int_0^\infty (1-F_X (t)) \, dt$ for every nonnegative random variable $X$ Remove Reviewer and Steward badges Badges should encourage good behaviour. But what when a badge encourages more bad behaviour than good?  We hear it all the time - robo reviewers, badge-hunters. The review system fights with that users that only want badges and not want to help.  There are many suggestions how to find such robo-reviewers or how to make it difficult to robo-review. But why not cut them off at the source? Don't make them want to review for badges at all.  Remove the Reviewer and Steward badges! The Custodian Bronze badge should suffice to bring a user to the review system. And we really only want users doing reviews who want to help and not doing it for the badges. "Pending" vs "Impending". Are they synonyms? They appear to me to mean almost if not exactly the same thing, but I am not sure. Are there differences in meaning between them? How to use ssh to transfer files from computer a to local computer I am trying to get some files off of my school Linux account using ssh. I have got the connection to work using:  scp &lt;school_server&gt;: ~/folder I want ~/where I want to go.    But when it goes to transfer folder it gives me the message:  not a regular file    The file contains .java files, and I want the whole folder. Find an example of a function sum $\sum_{n=1}^\infty u_n $ that converges   uniformly on $[a,b]$ and converges absolutely pointwise, but   $\sum_{n=1}^\infty |u_n| $ doesn't converge uniformly on $[a,b]$.   This seems pretty straightfoawrd but it's really hard to find an example. The choice of $u_n$ must be very specific. You can actually prove any power series wont work (due to Abel's theorem)  In addition, in order to prove the uniform convergence, $u_n$ must not satisfy Weierstrass' M-Test (because then $\sum |u_n|$ would converge uniformly aswell) I am working on a SQL query that reads from a SQLServer database to produce an extract file. One of the  requirements to remove the leading zeroes from a particular field, which is a simple VARCHAR(10) field. So, for example, if the field contains '00001A', the SELECT statement needs to return the data as '1A'.  Is there a way in SQL to easily remove the leading zeroes in this way? I know there is an RTRIM function, but this seems only to remove spaces. How do you split a list into evenly sized chunks? I have a list of arbitrary length, and I need to split it up into equal size chunks and operate on it. There are some obvious ways to do this, like keeping a counter and two lists, and when the second list fills up, add it to the first list and empty the second list for the next round of data, but this is potentially extremely expensive.  I was wondering if anyone had a good solution to this for lists of any length, e.g. using generators.  I was looking for something useful in itertools but I couldn't find anything obviously useful. Might've missed it, though.  Related question: What's the purpose of two capacitors in parallel? What's the purpose of the two capacitors in parallel on each side of the regulator in      I've seen similar setups in other similar circuits and can guess that it's related to one being polarized an one not, but I don't really understand what's going on there. Using zypper, how can I remove all packages installed from a specific repository? Show that the Sorgenfrey line does not have a countable basis. I am trying to understand this proof from Munkres' book which shows that the Sorgenfrey line does not have a countable basis. His proof is:  Let $\beta$ be a basis for $\mathbb{R}_l$. Choose for each $x$ an element $B_x \in \beta$ such that $x \in B_x \subset [x, x+1)$. If $y$ is not equal to $x$ then $B_y \neq B_x$ since inf($B_x$) = $x$ and $y$ = inf($B_y$). Therefore $\beta$ must be uncountable.   I am new to topology so I am probably just missing a simple point but I do not see why $\beta$ must be uncountable according to this argument. I agree that $B_y \neq B_x$ but isn't it possible that $y \in B_x$ (and thus the set $B_y$ is not needed as part of the basis)? Thanks in advance for your help. Is there any table or any other way(metadata/rest api) we can query the list views of a particular object that a user/group  has access.  Example:  SELECT Name FROM table_x WHERE UserOrGroupId = '1234..' AND  SobjectType = 'Account'   I can see an object named UserListView in workbench, but query on that returns no data. Is it deprecated? Can't insert code in my beamer slide I want to put some PHP code in my slide with the package listings but I have this error message:  Argument of \frame has an extra }.&lt;inserted text&gt;\par }   My latex code :   \documentclass{beamer}  \usepackage[utf8]{inputenc}  \usepackage[T1]{fontenc} \usepackage[frenchb]{babel} \usepackage{setspace} \usepackage{color} \usepackage{listings}  \usetheme{CambridgeUS}   \begin{frame} \begin{large}     Contexte : \newline \pause \end{large}  \begin{itemize}     \item Avertir Drupal \end{itemize} \begin{lstlisting}  // Gestion du contexte ete2013 // Utilisation d'un nouveau template if (%variables['ctpage'] == "ete2013") {     variables['template_files']=array('page-ete'); } \end{lstlisting} \end{frame} Not only in ortho: top, front, back.  Please don't link this answer   I want a background image like this guy has -> Find executable files recursively I have got the directory called Test and a few directories inside it. Both Test and the directories inside it have executable files. I'd like to print them with ls. I'd use this command.  ls -l `find Test/ -perm /u=x,g=x,o=x -type f`   Is this a good/right/quick command or not?  My solution is:  find Test/ -executable -type f -exec ls -l {} \;   and got the same result as warl0ck and pradeepchhetri offered. Calculating the longest distance within polygon in QGIS I want to calculate the "diameter" of polygons in QGIS.  The "diameter" defined as the distance between the two most distant points of the polygon.  I couldn't find a fitting solution in the field calculator. Maybe you have some ideas? One who has potential, but never gives the effort to show it.   What would be the best word or words that match this description? Why is Main method private?