There are some one-way transparent glasses.  Light can pass the glass in this way, but cannot in the other way around.   It is quite contrary to the experience that the path of light is reversible.   So what is the reason behind?
How does a  work? If seen from the outer side, we can see through thinking it is transparent, while if seen from the inside, the glass acts as a mirror. How?
I would appreciate if someone could help me write the mathematical equation for the seasonal ARIMA (2,1,0) x (0,2,2) period 12. I'm a little confused with how to go about this. I would prefer an equation involving $Y_t , e_t, θ$ and $Θ$. Consider the factorization into irreducibles of $6$ in $\mathbb{Z}[\sqrt{-5}]$. We have $6=2 \times 3$ and  $6=(1+\sqrt{-5}) \times (1-\sqrt{-5})$, i.e. $2$ distinct factorizations. And,  $$6^2=3 \times 3\times2\times2$$ $$=(1+\sqrt{-5}) \times (1-\sqrt{-5}) \times (1+\sqrt{-5}) \times (1-\sqrt{-5})$$ $$=(1+\sqrt{-5}) \times (1-\sqrt{-5})\times3\times2.$$ More generally, $6^n$ will have $n+1$ distinct factorizations into irreducibles in $\mathbb{Z}[\sqrt{-5}]$ by a simple combinatorial argument. But, can we construct a ring in which there exists an element that has an infinite number of distinct factorizations into irreducibles? To make life harder, can we construct an extension of $\mathbb{Z}$ in which this happens? I have been thinking about this for a while and have managed to find no foothold.. Any help is appreciated. I'm hoping there's something in the same conceptual space as the old VB6 IsNumeric() function? Which year does Spider-Man: Homecoming take place in? The first scene of the movie is presumably set in the immediate aftermath of The Avengers. The movie then fast-forwards to '8 years later'.  But Spider-Man already appeared in Civil War as a high school student, which he still is in this movie. So what's the timeline here? If Avengers was set in 2012 and Civil War in 2016, how can Homecoming be in 2020?  Or am I wrong in assuming the canonical timelines of the other movies? Example where union of increasing sigma algebras is not a sigma algebra My laptop running Windows 7 Ultimate (non OEM) died on me today and it has tonnes of stuff on it - my projects, Visual Studio and office installations, etc. etc.  I am getting a new laptop from somewhere and was wondering if I could just unplug the hard disk from my original (dead) machine and plug it into the new one.  I remember trying this once with Windows Xp (on a desktop) and the OS crashed on boot and I had to reinstall everything again.  I have read about  but by the looks of it, it can be used only when the host computer is alive and kicking -- which mine isn't.  My old laptop was a Compaq Pressario v3000 (3 years old) on an AMD and the new one is going to be a new dual core Intel HP laptop.  Any ideas?  Thanks! How do you refer to a hyponym that is the same word as the hypernym? What word (or how do you phrase things) do you use when the ostensible word for the class is the same as the word for a subset of the class?  For example, in the United States, there are many brands of sugared, carbonated soft drink that one can buy: Coca-Cola (or Coke), Pepsi, RC Cola, Sprite, 7-Up, A&amp;W or Mug Root Beer, etc). The first two are kinds of 'coke' or 'cola' (but no one says 'cola').  , one asks for any type of such drink as 'coke'. How does one then ask for the particular kind of 'coke' that is 'Coke' (pronounced the same)? Does one reduplicate and say a 'Coke coke', does one repeat with emphasis (or without), does one use a different word like 'coca-cola' (co-cola), or what?  The (perceived) difficulty (surely those in the South are able to get the drink they want somehow) isn't limited to there. Where the drink is called 'soda', if you ask for a 'coke', you'll still sometimes have the choice among Coca-Cola, Pepsi, etc. "Can I have a Coke?" the response might be "Is Pepsi OK?". "Sure, Pepsi, Coke, whatever." You don't use 'cola', you just ask for the particular kind and hope the listener will help differentiate.   Given these multiple strategies for disambiguating, what do you do say to get a 'Coke' in the southern US? are there any other examples of a hypernym being the same as the hyponym, and so creating a disambiguation problem? Background Video is shown in Rendered mode but not when szene is rendered I have hundreds of excel files which are all of the same format (i.e. 4 worksheets per Excel file). I need to combine all the files into 1 all singing and dancing file which must have the same format as the originals (i.e. maintain the four separate worksheets, which are all identically named).  While each file is structured the same, the number of columns (and the heading names) between sheet 1 and 2 (for example) is different. So it can’t be combined into one file with everything in one sheet!  There are two complications:   I need to create an EXTRA column in the merged file (on EACH sheet) to identify the source file (“file name”). The files contain a lot of zero data entries (e.g. 55 rows of useful data followed by hundreds of rows of zeros) which I need to remove from the merged file.   I’ve never used VBA, but everyone has to start somewhere I suppose. Java - Splitting a CSV file into an Array Intuition for Rayleigh PDF We have ground-truth data $\mathbf{x}^* = (0,0)^T \in \mathbb{R}^{2}$. Furthermore, we have $N$ measurements $\mathbf{x}_i \in \mathbb{R}^{2}, i\in \{1,\ldots,N\}$. We calculate the $N$ error vectors $\mathbf{e}_i = \mathbf{x}_i - \mathbf{x}^*$. We assume that the two components of $\mathbf{e}_i = (e_{x,i}, e_{y,i})^T $ are independent of each other and normally distributed with equal mean $\mathbf{\mu} = (0,0)^T$ and variance $\sigma^2$. The absolute errors $e_i = \sqrt {e_{x,i}^2 + {e}_{y,i}^2} $ follow a Rayleigh distribution, is that correct?  The probability density function (PDF) of the Rayleigh function is zero at a value of zero. Why is this the case (intuitively)? I would assume that our errors should most likely be 0 (i.e. PDF should be highest at 0)... How do I execute a file from a FAT USB drive? I'm trying to install a portable app onto my USB drive such that it is compatible with both Ubuntu and Windows (specifically, a program called eToys). Support is already built into the app for both operating systems - there's etoys.sh for Ubuntu and etoys.exe for Windows. I decided to install onto a FAT drive since that can be read from both systems. This works fine for Windows, but for some reason I cannot execute etoys.sh on Ubuntu.  The problem is not with the file - when the whole folder is copied to the local hard drive, the app works great in Ubuntu. But when I try to execute it from the USB, it opens the file in a text editor.  I then tried to run it from a terminal, but I got the message Permission denied.  I've had the same problem with other executables as well.  Is there an easy way to execute things from a USB stick? Why couldn't the Jedi detect Senator Palpatine as having powers? In Return of the Jedi, when trying to sneak into the base on a shuttle, Luke said he senses Darth Vader's presence and said he shouldn't have come lest he jeopardize the mission. Darth Vader also sensed Luke, but let him in anyways. Also, Yoda and Obi-Wan could detect the Force in young Anakin.  So if Jedi and Sith can detect each other, why couldn't they detect Senator Palpatine to begin with? It seems like a giant plot hole. The  is a proposed propulsion mechanism for spacecraft in which some form of microwave device provides the propulsion. The consensus from the physics community, including many voices on this site, is that the proposed device would violate conservation of momentum.   Several experiments have been conducted, by three main groups: (i) , from Satellite Propulsion Research Ltd, (ii) a research group at the Northwestern Polytechnical University in Xi'an, China, and (iii) Eagleworks Laboratories at NASA's Lyndon B. Johnson Space Center in Houston, Texas. However, few of these experiments have been performed in vacuum (and none of the vacuum tests has been published in a peer-reviewed journal), which means the effect of air currents around the device cannot be ruled out.  This device has been the subject of many questions on this site, including          and their many closed duplicates.  Many of these questions ask what the proposed explanations are, but then veer off into territory of the form "assuming it is true, how does it work?", so they have been (rightfully) closed as counterfactual physics. I feel this sort of bundling does a lot of harm to the discussion, and there is some scope to ask what exactly is being proposed as an explanation. So:     What do the proponents of EmDrive claim is the theoretical justification of the device's function?   Please limit answers exclusively to references, and indicate whether they are peer-reviewed or not. Please limit answers to serious attempts at explanations, as opposed to vague claims about the 'quantum vacuum' - or indicate if an experimental paper does not have any such theoretical explanation or reference.  To be clear, this is not the place to discuss whether the explanations are correct or not. If you have specific questions about any of these sources, ask it separately. (However, if your question starts with "assuming that this works", be prepared for it to be closed.) If you feel there are not enough resources on this thread, you can  but please do not post another question asking people to look for more references. Which "href" value should I use for JavaScript links, "#" or "javascript:void(0)"? The following are two methods of building a link that has the sole purpose of running JavaScript code. Which is better, in terms of functionality, page load speed, validation purposes, etc.?    function myJsFunc() {     alert("myJsFunc"); } &lt;a href="#" onclick="myJsFunc();"&gt;Run JavaScript Code&lt;/a&gt;     or    function myJsFunc() {     alert("myJsFunc"); }  &lt;a href="javascript:void(0)" onclick="myJsFunc();"&gt;Run JavaScript Code&lt;/a&gt; Drop "not constructive", combine "noisy", reword "rude" and "other" comment flags My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M Using Static Variables in a Custom Module I'm trying to define a static variable for use in my custom module. I want it to let me pass a number from function to function. I'm using drupal_static() but I can't get it to work. How do I do this?  This is the code I'm using to define my static variable.  $var = &amp;drupal_static(__FUNCTION__); if (!isset($var)) {   // generate contents of static variable   $var = '8'; } return $var;   I've tried putting it in a custom module.    function viewusercontact_locateuser($value, $key, &amp;$counter) {    global $user;     /**********In here***********/     if ($value['uid'] == $user-&gt;uid) {       ........    } }   I can't seem to get it to work. What am I doing wrong?  (I got my code from the following guides) Why is the application of probability in  (QM) fundamentally different from its application in other areas? QM applies probability according to the same  as in other areas of physics, engineering, etc.  Why is there a difference?  Naively one would assume one of these possibilities:   It is not the same probability (theory?) It is a matter of interpretation (of the formalism?) Something else?   Many answers (which I am still studying) focus on the fact that the combined probability of two mutually-exclusive events in QM is not equal to the sum of the probabilities of each event (which holds classically by definition). This fact (appears to) makes the formulation of another probability (a quantum one) a necessity.   Yet this again breaks down to assumed independent, if this is not so, the "classic probability" is applicable (as indeed in other areas). This is one of the main points of the question. How do I move my website to a new server without interruption to email?