I've grown curious about the phenomenon of light interference. If two light sources of different wavelengths that correspond to two arbitrary colours, say blue and yellow, constructively join, they will result in a green central fringe, as any colour mixing chart would tell us. Is this because the two electromagnetic waves add up and create a new wave with the colour yellow, or is it just our brains tricking us into seeing a merged colour? (As many colours are made-up and not physically real, like pink, for instance). Thanks so much in advance.
So, when someone is red-green colorblind, the colors appear the same to them, like this:   And if you're totally colorblind, then things presumably just appear like they would in a black-and-white movie.  However, this isn't how ultraviolet patterns seem to work. Compare how we see this flower to the version where ultraviolet is visible:   The UV pattern is completely invisible here. However, unlike with the red and green, this isn't because yellow and UV are colors that appear identical when you can't see UV. Look at these flowers:     This time the flowers are purple, but the UV pattern is still invisible. Why is that? Shouldn't the UV pattern still be apparent on at least one of the flowers, just in a different color? And on some other flowers, the UV does appear as a different color. So:    Why is the UV invisible only sometimes?  Does it have to do with the flower using iridescent structures to produce color, instead of a pigment? Can this happen with red and green, as well?
Start a new process without blocking the terminal Is it possible to do this? For example if I run "gedit tifatul.txt" via the command line, my terminal becomes blocked and I can't enter other command in this terminal before I quit gedit. Can I start a program (like gedit) without blocking the terminal? In windows I think this can be done like "start notepad tifatul.txt" My question is how I can intergrate Salesforce with different FTP servers in real time. I have read some articles about it, but to be absolutely sure I thought it would be a good idea to post a question here.  I want to be able to send and receive data from Salesforce as a csv file to a ftp server. How I'm thinking about doing this is listed below.  Send the data:  Create a apex class which query the necessary data in Salesforce and create a csv file. I guess this is trivial? Then send the file to a web service created in Salesforce, just by calling it in the apex code. Create a web service in Salesforce which receives the data from the apex code. This web service should in some way send the data to the appropriate ftp server. I guess I can simply modify some of the code provided by Salesforce to make this work? The file is sent. Receive the data  This one is a bit trickier. I guess I have to pull the data from the FTP server by using my web service, which then send the file collected to the appropriate apex class. Or, the FTP server could send the data to the SFDC web service, I don't know if this is possible? The web services on the other side that sends the data to the ftp server, could send it directly to the SFDC web service, which then again forward it to the apex class. I guess the web service will use the remote site url to connect to the SFDC web service? Have a web-part display only sub-folders? I am new to SharePoint 2013. I was curious how to put a WebPart for a Document Library on a page with SharePoint 2013, not 2010.   This WebPart would then show the content of a specific library folder and not start at the root of the folder. So say I have a library with multiple folders like "Marketing", "Finance" etc,   I want to be able to create a web part that would only show the contents within the “Marketing subfolder and all of it contents. Is this possible? Which is more idiomatic in a bash script: `|| true` or `|| :`? I don't do terribly much shell scripting, so I was a little surprised when I was reading  and I saw the syntax they used in this documentation:     A non-zero return from the command in any submodule causes the processing to terminate. This can be overridden by adding || : to the end of the command.   I had to look up that || : was a shorthand for forcing a command to exit successfully.  Anytime I've had to make a command exit successfully, I used || true.  Is || : considered to be more idiomatic? Clarification on Rayleigh scattering causing various sky colors (I know Rayleigh scattering isn't the only reason why the sky is blue but to simplify the question lets focus on that)  The commonly stated reason for why the sky is blue is that smaller wavelengths are scattered more easily off the molecules in the air. During the day, because the blue light is scattered more, the sky is illuminated more with that blue light and more reaches your eyes. However, during sunsets and sunrises, the light from the sun must travel a longer distance. The explanation I have found is that the blue light is scattered away and more of the longer wavelength reds and greens are available to reach your eyes to get those warmer colors, (red and green of course mixing to get yellows).   My question is that it seems like these explanations are conflicting. If the light at sunsets and sunrises travels more distance, why won't the blue light be scattered even more and thus illuminate the sky with blue light more than in the daylight? It confuses me that in one case the scattering of blue light causes the sky to be blue but then at sunset the scattering eliminates this color. Could I get some explanation on this? Isomorphism of quotient modules implies isomorphism of submodules? Let $A$ be a commutative ring, $M$ an $A$-module and $N_1, N_2$ two submodules of $M$.  If we have $M/N_1 \cong M/N_2$, does this imply $N_1 \cong N_2$?  This seems so trivial, but I just don't see a proof... Thanks! What is the logical form of the definition of validity? My text book gives the definition of validity as "An argument is valid IFF if the premises are true, then the conclusion must be true". Using a conditional elimination on the RHS of the IFF yields "An argument is valid IFF the premises are false or the conclusion is true".   Yet, this seems strange to me. Am I doing something incorrect with my manipulation or is this definition actually true? Surely the criteria for a valid argument goes beyond a false set of premises or a true conclusion. Shapefile layer no longer editable (toggle edit option greyed out) in QGIS? How to save animation as a video format I am basically trying to make an intro for my youtube channel. I am sort of familiar with the program because I was playing around with it for a long time, getting the basics of it. With the help of youtube videos I am basically done with my project. I put my name in it and everything. I just need to know how to save the animation onto my desktop as a file that I could open and would be in a video format. How to prevent LaTeX from hyphenating the entire document? I can't find where I can remove any kind of hyphenation and just have LaTeX just do a line break.  edit: Honestly speaking I just don't like to read hyphenation anywhere and that's the only reason why I wanted to remove it. It is a matter of style, probably unexpected in LaTeX.  The document has only a summary in a different language and I used the language packages to hyphenate properly. Show sub reasons in close review queue Currently close vote review queue shows the top level close reason in the header, but some close reasons, for instance, off topic have very different sub reasons. For instance, "demonstrate minimal understanding" is different from "This question belongs on a different site in the stack exchange network".  It would be nice if sub close reasons were also shown. sed command not giving proper output for regular expression used I am trying to fetch data between a range of time intervals from the log file. However, the complete data is not fetched for the end date.  Below is the command used:   sed -n '/26/Nov/2018/,/30/Nov/2018/ p' /path/file.log    The data I am having in the above log file is somewhat like:   192.168.0.123 - - [25/Nov/2018:13:24:59 +0530] "Data 1"  192.168.0.123 - - [26/Nov/2018:13:24:59 +0530] "Data 2"  192.168.0.123 - - [26/Nov/2018:13:25:09 +0530] "Data 3"  192.168.0.123 - - [27/Nov/2018:13:25:09 +0530] "Data 4"  192.168.0.123 - - [27/Nov/2018:13:25:11 +0530] "Data 5"  192.168.0.123 - - [27/Nov/2018:13:25:53 +0530] "Data 6"  192.168.0.123 - - [28/Nov/2018:13:25:53 +0530] "Data 7"  192.168.0.123 - - [29/Nov/2018:13:25:53 +0530] "Data 8"  192.168.0.123 - - [30/Nov/2018:13:25:53 +0530] "Data 9"  192.168.0.123 - - [30/Nov/2018:13:25:53 +0530] "Data 10"  192.168.0.123 - - [01/Dec/2018:13:25:53 +0530] "Data 11"  192.168.0.123 - - [01/Dec/2018:13:25:53 +0530] "Data 12" CASE WHEN with GROUP BY I have a table that looks like this (oversimplified case of the actual case to make my point)  CREATE TABLE sales (    id int,    currency VARCHAR(5),    price int    shop_id int );   Now I need to make a query that will give me something like this table, grouping by shops yet giving sum of sales per currency My problem is when I make currency column non aggregate it fails because my query becomes non standard. When I add currency to group by then each currency creates new row, something I don't want. I have run out of option and would appreciate any help or pointer to the right direction.  I use MySQL but would appreciate if I would get the solution that works with more databases (PostGreSQL being at the top of the list after MySQL)  Query that works with undesired results  SELECT   shop_id,           (CASE WHEN currency= "GBP" THEN SUM(price) ELSE 0 END) AS POUND,           (CASE WHEN currency= "USD" THEN SUM(price) ELSE 0 END) AS USDOLLAR GROUP BY shop_id, currency   The data that should be produced by the query  shop_id     |   POUND   |   USDOLLAR     -----------------------------------------     1       |   400     |   300 -----------------------------------------     2       |   250     |   100 -----------------------------------------     3       |   400     |   100 ----------------------------------------- How to make a cyclorama I can create a collection of pictures giving a 360-degree view from a certain spot, just taking a bunch of photographs from the same spot but in a different direction.  However, what software could I use (on Windows) to stitch these images together to get one big image?  I prefer something that would stitch them together without showing any seams. During my studying to integration I find this integration.  So I tried to prove but I got stuk.  So I need help in this integration.  $$\displaystyle\int_{-\infty}^{\infty} \frac{x \sin (x)}{1+x^2}  dx = \frac {\pi}{e} $$ At WWDC 2018 macOS 10.14 or macOS Mojave was disclosed.  I am currently on macOS Sierra (10.12) and am looking forward to upgrading to macOS Mojave once its released.  I was wondering if it will be possible to update to macOS Mojave without converting to APFS, similar to  trick from OS X Daily on how to upgrade to macOS High Sierra (10.13) without converting to APFS with the command /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall --converttoapfs NO. I've been using the Linksys USB6300 Adapter but when I switched to Ubuntu it stopped working since its only compatible with Windows. I've tried using ndiswrapper and although it says my windows driver is installed, my device isn't showing up. Anyone know how I could get this wireless network adapter working? Thanks.  lsusb  Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 012: ID 05c6:6766 Qualcomm, Inc.  Bus 001 Device 006: ID 0bda:0153 Realtek Semiconductor Corp. Mass Storage Device Bus 001 Device 005: ID 05e3:0608 Genesys Logic, Inc. USB-2.0 4-Port HUB Bus 001 Device 004: ID 04ca:007d Lite-On Technology Corp.  Bus 001 Device 003: ID 04ca:008a Lite-On Technology Corp.  Bus 001 Device 010: ID 13b1:003f Linksys  Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Some Windows 10 UWP icons not displaying on search, or in settings I'm adding a title clock in the foot line of a beamer slide, if I compile it with pdfLaTeX it works fine; while the clock doesn't align in the middle vertically if compiling with XeLaTeX. How can I fix this.  Here is my MWE:  \documentclass[10pt]{beamer} \usepackage[font=Times,timeinterval=1]{tdclock} \usetheme{Madrid} \title{Title} \author{Authors} \institute{Institute} \date[\initclock\tddate\ \ \tdtime]{\today} \begin{document} \frame{\titlepage} \end{document} What do you call somebody who asks a question and somebody who answers a question?