In current quantum models, name one or more objects that collapse an entangled waveform into a single classical particle other than a complete living human person.  The "duplicate" I just read has an accepted negative score answer that starts with "An observer is a person...", so I don't know how to make this simpler. If you are interested in jokes related to the issue, continue reading, but otherwise you may begin formulating an answer now.  Here are some examples of solid answers that, while not true, would answer my question if they were in a modern quantum model:   Anyone with a full head of hair is an observer.  Receding hairlines have a reduced probability of collapse.   Wigs count too. Anything with a phone number is an observer; it doesn't matter to the quantum state if anyone picks up.  The classical result and its delta T depends on your carrier, and all possible states use the data plan simultaneously.  Anything that walks on two legs is an observer.  Sorry dolphins.  And you can't just do it sometimes, it has to be your primary mode of transport, so no weasling your way in, dogs. It doesn't quantize until it's published in Nature.  PNAS doesn't work, and we all know the news can be both true and false simultaneously now. God (not yours, the other one) decided that some things should act classical, and entangled quantum stuff is so impressed with the endorsement when they come into contact, it acts like a classical thing from that point forward. The electron over there on your keyboard and/or phone is actually the one and only observer.  Its potential paths look like observers now, but as soon as you touch it, we all disappear.   Include as much math as it takes.  A greek letter with a hat that does the job is fine.  Just no humans in your theory.  Like teaching it to a millenial, one might say.  There may be follow up questions, but it is not necessary to answer them to my satisfaction to receive check mark.
My question is not about (pseudo) philosophical debate; it concerns mathematical operations and experimental facts.  What is an observer? What are the conditions required to be qualified of observer, both mathematically and experimentally?
Recursively delete empty directories in Windows We know that the addition and multiplication operators are both commutative, and the exponentiation operator is not.  My question is why.  As background there are plenty of mathematical schemes that can be used to define these operators. One of these is   where $H_0(a,b) = b+1$   (successor op) $H_1(a,b) = a+b$   (addition op) $H_2(a,b) = ab $   (multiplication op) $H_3(a,b) = a^b$   (exponentiation op) $H_4(a,b) = a\uparrow \uparrow b$   (tetration op: $a^{(a^{(...a)})}$ nested $b$ times ) etc.    Here it is not obvious to me why $H_1(a,b)=H_1(b,a)$ and $H_2(a,b)=H_2(b,a)$ but not $H_3(a,b)=H_3(b,a)$  Can anyone explain why this symmetry breaks, in a reasonably intuitive fashion?  Thanks. I don't know which buttons I have to click or what key combination to type to calculate a cube root. Proof that $\cos(\pi/3)=1/2$ Is it possible to prove that $\cos(\pi/3)=1/2$ without using any trigonometric identities?  To be specific, my calculus-book simply states that with an angle of $\pi/3$ on the unit-circle the points (0,0) and (1,0) are the vertices of an equilateral triangle with edge length 1. But how can one reach such conclusion?  Thanks! I would like to declare functions in tikz for multiple uses of the same function within the code.  Sadly, it seems that the tikz "declare function" is not compatible with the french option in babel. Indeed, the following code (that I simplifed on purpose) runs fine :  \documentclass[english]{article} \usepackage{babel}                       \usepackage{tikz}  \begin{document} \begin{tikzpicture}     \tikzset{declare function={Carre(\t)=\t*\t;}}     \draw plot [domain=-1:1] (\x,{Carre(\x)}); \end{tikzpicture} \end{document}   But when I replace   \documentclass[english]{article}   with   \documentclass[english,french]{article}   compilation generates an error. This is what the log file says :     Missing character: There is no = in font nullfont!   Missing character: There is no @ in font nullfont!   Missing character: There is no @ in font nullfont!      Runaway argument?   -1:1] (\x ,{Carre(\x )}); \end {tikzpicture} \end {document}    ! Paragraph ended before \pgfmath@local@@functions was complete.                          \par    l.18       I suspect you've forgotten a `}', causing me to apply this   control sequence to too much text. How can we recover?   My plan is to forget the whole thing and hope for the best.   Before posting this, I updated all packages without success.  Any help welcome! Duplicate objects transformation applies to both objects I'm facing this frustrating "feature" that I can't seem to remedy; when I duplicate an object (and now, even when I create two completely new objects), their transformations/scaling is synchronized. This is extremely annoying when trying to use any sort of transformation keyboard shortcut.  It should be noted by going to the properties menu (N) and manually setting the properties works just fine.  For instance, here is just the camera selected (trust me, I made sure):   And when I try to transform by clicking+dragging on the X axis OR by hitting G->X, this happens:   They are not grouped (verified by going to the Groups list up in the Scene panel) and they do not have parents (verified by going to Object->Relations).  I have tried the unlink command as well, to no avail.  I have seriously run out of options; what did I change to have my G->X shortcuts transform multiple objects? It seems completely at random, too; certain objects seemed to be "linked" to other random objects, and this "linking" is guaranteed when duplicating even when I do a non-linking duplicate (Shift+D).  What gives? What is the point of the `cd` external command? Install macOS Sierra on VirtualBox? I’m trying to install macOS Sierra on VirtualBox, but can’t seem to make it work. For reference, here are the steps I took.   Downloaded the Install macOS Sierra app from the App Store. Used the inbuilt media creation executable, CreateInstallMedia on a disk image. Created a new VM with the default settings for an OS X El Capitan, plus 128 VRAM. Since VirtualBox refused to accept the DMG, I tried splicing out the InstallESD. VirtualBox now accepted it, but wouldn’t boot. I tried to boot through rEFInd, but still no luck. I tried to patch it both ways (base system and ESD) with iesd. No luck. When booting to GParted LiveCD, it flat-out refused to discover any of the installer CDs.   How can I patch the installer to work with VirtualBox? I don’t want to use pre-patched versions of either the installer or an existing installation, as though to avoid piracy. Why is the light reflected at the same angle from mirror? From the school physics I know that the material objects bounce from the plane surface at the same angle, losing some kinetic energy. In the same school I was taught that the light (and waves in general) obeys this principle too.  Obviously, in the case of light the plane surface should be a perfect mirror. But I can't understand how should this work from the quantum point of view. Let's assume that our mirror consists of a single silver atom.  Why should the electrons of this atom re-emit consumed photons at some specific angle? Someone has pointed their domain (www.bomberball.net) to the same IP as my domain (www.kapparate.com) , and Google is now showing the former when searching for Kapparate, rather than the latter. What's the best way to block requests coming from www.bomberball.net ? Is it positive or negative for the average website to allow search engines to index user comments? I've been trying to answer this question myself by researching and searching on google but I haven't been able to come with a final answer. I have some hypothesis I would like share anyway:   The average website intends to reach the higher audience possible. User generated content by comments is an efficient way of increasing the relevance and the valuable information of the average website. Indexing comments will make any site attractive to spammers. Indexing comments is more convenient for new/low-traffic websites than it is for old/high-traffic websites. The web in general is currently choosing not to index comments in the average website because of fear to the SPAMMERS. The average author of a content-valuable comment would like his comment to be indexed Not indexing comments discourages the creation of content-valuable comments.   So, what do you think finally? Is it positive or negative for the average website to allow search engines to index user comments? Why? Rewrite code to make it faster Amazon RDS - Online only when needed? Why is rabies incurable? I'm still not sure about the mechanics that lead to rabies being incurable. I know that it can be treated before any symptoms show up, but why is it that once symptoms show the person is a dead man walking? Linear mixed effect model interpretation with log transformed dependent variable I have a dataset in which the response variable is non normal, but on log transforming, it follows the normal distribution. I constructed a mixed effect model using lme4::lmer() as below (multiple measurements within each region), where A is a continuous variable and there are 7 regions  model&lt;-lmer(log(response)~A + (1|Region), data, REML=FALSE)   My output is   Linear mixed model fit by maximum likelihood . t-tests use Satterthwaite's method ['lmerModLmerTest'] Formula: logresponse ~ A + (1 | Region) Data: df[, -c(6)]   AIC      BIC   logLik deviance df.resid  151.8    159.8    -71.9    143.8       51   Scaled residuals:   Min       1Q   Median       3Q      Max  -2.24856 -0.63631  0.02206  0.59999  1.94895   Random effects: Groups   Name        Variance Std.Dev. Region   (Intercept) 0.8611   0.9280   Residual             0.5814   0.7625   Number of obs: 55, groups:  Region, 7  Fixed effects:               Estimate Std. Error        df t value Pr(&gt;|t|)   (Intercept) -1.112047   0.747373 19.651457  -1.488   0.1526    A           0.008585   0.004250 29.157266   2.020   0.0526 .  Correlation of Fixed Effects: (Intr) A -0.871   1) Would I infer that for A effects the response variable and the response increases by exp(0.008585) +/- exp(0.004250) (std error)? Would that be the right interpretation?  2) exp(Intercept) is not equal to the mean(log response). They are close but not equal. Why are they not equal and should I be concerned?   I know that this is a hard question to answer without knowing the dataset. So please suggest how I can improve the question. Minimum value of $\left(a+\frac{1}{b}\right)^2+\left(b+\frac{1}{c}\right)^2+\left(c+\frac{1}{a}\right)^2$ Given $a,b,c \in \mathbb{R^+}$ such that $a+b+c=12$   Find Minimum value of $$S=\left(a+\frac{1}{b}\right)^2+\left(b+\frac{1}{c}\right)^2+\left(c+\frac{1}{a}\right)^2$$  My Try: By Cauchy Schwarz Inequality we have  $$\left(a+\frac{1}{b}\right)+\left(b+\frac{1}{c}\right)+\left(c+\frac{1}{a}\right)\le \sqrt{3}\sqrt{S}$$  $\implies$  $$\sqrt{3S} \ge 12+\frac{1}{a}+\frac{1}{b}+\frac{1}{c}$$  Now by $AM \ge HM $ inequality we have  $$\frac{a+b+c}{3} \ge \frac{3}{\frac{1}{a}+\frac{1}{b}+\frac{1}{c}}$$ $\implies$  $$\frac{1}{a}+\frac{1}{b}+\frac{1}{c} \ge \frac{3}{4}$$  hence  $$\sqrt{3S} \ge 12+\frac{3}{4}=\frac{51}{4}$$  hence  $$3S \ge \frac{2601}{16}$$  so $$S \ge \frac{867}{16}$$  is this approach correct and any better approach please share. Links in site profiles stripped from network profile I have a link in my profile, advertising a Stack Exchange question of mine (which I believe is acceptable use of the profile page). The link works fine on my individual profile pages. For example,  and . However, on  the links do not show.  The link is present on the GIF and on the text (two separate links, both to the same place). Both work fine on the individual profile pages but both are absent from the network profile page. The GIF and text are present, just without being linked.  Is there a reason for disallowing links from the network profile page, or is this a bug? Read Gif Images using WebView android How to interpret these acf and pacf plots Going through the spells, I see the phrase "Willing creature" used to determine who you can cast some spells on. I don't ever see a proper definition of what a willing creature is, but I would assume that it would go something like if you asked them "Can I perform this spell on you" they would answer yes. Is there a more formal definition of what makes a target willing in 5e?  What are the ways I could make an otherwise unwilling creature willing? Suggestion spells, for instance, should probably work but what other options do I have?