I consider a very large non homogeneous cloud of dust in isolation. No external gravitational interactions. It is initially completely still and start collapsing under the its own gravity.  Can the separate gravitational collapse of denser subparts, interacting with the rest of the cloud, induce spinning motion in some of these subparts?  To avoid consideration of limit conditions, the cloud may be considered infinite.  I am interested in an answer primarily in Newtonian mechanics. But if relativity can change the answer, that is interesting too, as a complement.  The same goes for quantum mechanics (though I doubt it is compatible with my stillness hypothesis). BUT, my primary interest is pure Newtonian mechanics.  I did some research on the site, and this question has not been asked or answered previously with the explicit precondition of initial stillness of everything, i.e. lack of any relative motion between any two parts of any size.  My prime motivation for asking it is that all questions regarding motion and (angular) momentum seems to be answered somewhat tautogically by: there is this motion because there is that motion, exchanging this for that here and there.  Of course. collapse does create motion. So the question is really about spinning motion and orbital motion.  My own belief, though I do not have the math to prove it formally, is that lack of homogeneity is enough to cause the emergence of angular momentum in equal opposite amount in different parts of the cloud, so that the total angular momentum remains null.
In an older question from June 2011, , apparently revived by the system, a user is asking about the origin of the rotation of celestial bodies.  The  (with 17 votes) states the following:     When things collapse under their own gravity in space (i.e. clouds of gas and dust), any small amount of asymmetry in the collapse will be enough start it spinning.   And then it goes on saying:     Even if it spins by a tiny amount, as it collapses, angular momentum     conservation will mean it spins more and more quickly.   Is all this really correct?  I could try to ask in a comment to the answer. I actually did. But the author is no longer registered.  Hence I am asking it as a question.  But that is not the end of the story. As I was about to ask my question, I looked for other relevant questions, and there are some. I did not make an exaustive survey, but I did not find one that had satisfactory answers:    (december 2011) has just one accepted answer (0 votes) stating essentially that the solar system has angular momentum because it started from a cloud that had angular momentum. No comment.  (july 2011) is questionning about everything from galaxies to electrons. The answers are of a much higher quality, but while they seem to justify the possiblility of spin and angular momentum (and its conservation), there are not clear on how it appears, at least for celestial bodies.  (june 2013): That was my own very naive first question on this site. It is related but does not directly address spin.   One answer I found is that momentum appear from bodies in relative motion past each other. Nice, but not really an answer: where did they get their relative speed to begin with. Unfortunately the answer is: from the angular momentum of larger structures they belong to (well, it can be more comples). So this is just chicken and egg explanation. But how did it get started?  Note that my question is not a duplicate, since it is primarily whether the above statements are correct, which is not considered in these other questions.  Furthermore, these questions are fairly old, and given that none had received answers that seem to answer the question of the origine of existence of celestial angular momentum (not in a way I can understand anyway), it may be appropriate to attempt restarting the process, with the above discussion to motivate that an answer should explain the physical mechanism that started the existence of spin of celestial bodies.
is a typical example for , though it is said that long time no see has been accepted by the mainstream English speakers.  Recently, there is a  movement in the , and a few new Chinglish words have been invented to demonstrate the characteristics of the Mainland.  The most outstanding examples (in my opinion) are:   shitizen - a citizen without citizen rights freedamn - the freedom for shitizens (no freedom) democrazy - the democracy for shitizens (no democracy) smilence - the speeches under the freedamn of speech () z-turn - to make effort in vain ( (Pinyin))   Here are my questions. Has there ever been any neologism movement in the history of English? What are the criteria to adopt new words into English? I have come across this .  Has anyone tried anything similar or does it work for you? Can you tell if an email customer / user enters is correct &amp; exists? Order of products of elements in a finite Abelian group Deleting Individual SE Accounts How does the garage system work in GTA V? how do i get my stolen phone& pictures back? On 7 july 15 someone broke in my house and stole my galaxy note 3 it did not have service it has been disconnect for about 6mo now i would like to get my phone back because it had picture of me and my dad who died the day after father day this past june &amp; other family pictures that can not be replaced.how do i go about getting those back? I have 5 tables and a section after them. After creation of an output file I have two tables on one page, then a section and last 3 tables on next page.  What I want to achieve is to put tables and section below them.  \begin{table}[ht]\footnotesize \centering \begin{tabular}{|ll|} ...... \end{tabular} \label{tab:result} \end{table}  \section{Section below tables} Here is a DOM-based XSS flaw reported by SalesForce Security Review team in our code:   RootComponent  &lt;aura:component extensible="true" abstract="true" access="global"                 description="Root template component"&gt;     &lt;!-- ... lot of other code ... --&gt;     &lt;aura:attribute name="label"                     type="String"                     access="global"                     description="Label of the form input element" /&gt;     &lt;!-- ... lot of other code ... --&gt;  &lt;/aura:component&gt;   SubComponent  &lt;aura:component access="global" extends="c:RootComponent"                  description="Child extension of RootComponent"&gt;     &lt;!-- ... lot of other code ... --&gt;     &lt;label&gt;{!v.label}&lt;/label&gt;     &lt;!-- ... lot of other code --&gt;  &lt;/aura:component&gt;   According to SFDC, "any app can extend SubComponent component and pass in  as a label and trigger a DOM-based XSS attack." The solution would be to "sanitize" label global attribute to avoid such attack. What is meant by sanitization of global attribute?  I tried to reproduce the so-called security flaw , but as label attribute is of type "String" , when we send it HTML, it is displayed as a string, not as interpreted HTML ... so I don't see where the security flaw could be :/  &lt;aura:application &gt;     &lt;aura:handler name="init" value="{!this}" action="{!c.doInit}" /&gt;      &lt;c:SubComponent aura:id="TestXSS" label="DOM-based XSS attacks" /&gt;  &lt;/aura:application &gt;   JS Controller  ({     doInit: function(component, event, helper) {         var XssAttack = '&lt;img src=x onerror=alert(1) /&gt;';        component.find('TestXSS').set('v.label',XssAttack);     } })   Output    We have global attributes everywhere. Our components are packaged and meant to be extended by client implementation. Do we actually need to sanitize them? What options do I have to replace a failed service panel? What are my options to replace an old service panel?   We had a terminal get burned up in our old 1960s GE (TRX2012S if it matters, it's a split-bus/rule-of-six panel).   The tech who looked at it said the part is no longer available, but that if I could find another old service panel just like it, he could swap in the part. Otherwise, it's going to be $2,000+ to replace it with a modern service panel, which also requires getting up to modern code, which involves a lot of other stuff.   EBay and Google isn't showing any direct replacements (or the flush-mount TRX2012F).    What other options would there be to replace the panel internals?  Are the screw mounting holes compatible with modern GE panel internals? Is the main breaker separable and could that be changed alone?    Enclosure dimensions are about 20.5" x 12". Front panel dimensions are about 22.25" x 14".  UPDATE:    I'm looking at information on replacing the breaker box myself. As the homeowner I wouldn't be required to update anything else to get up to code. Does this sound like a good idea? I've done minor electrical DYI work but nothing this involved.  PICTURES:            More pictures: I am pretty sure that this is such a stupid, stupid question, but how do you prove that $d_2(x,y)={|x-y|\over {1+|x-y|}}$ satisfying the third condition to be a metric, which is the triangle inequality.   I know that I should really be able to do this, but I just can't, I keep seeing a contradiction. Please help me. Modifying cat command to number paragraphs and display last paragraph only I have a text file for which I need to do three things:   Modify the "cat" command to highlight keywords whilst showing the complete contents of the file.  Modify the "cat" command to automatically number the paragraphs. These are separated by a single blank line.  Modify the "cat" command to display the final paragraph only.    The tricky part is that all of these need to be done by modifying the cat command.   I've seen many forum posts explaining that cat is not meant for this - and I can entirely see why. However, the challenge is that I have to use cat! Unable to delete recup_dir.1 folder A folder was created when I used a utility to recover pictures from a cd card that I deleted by mistake.  Now I can't delete it or move it. I am told I am not the owner of it even when I am logged on as root.  How can I delete the recup_dir.1 folder from my machine? I would like to hide all items that I don't need from appearing in App Lens.  For example: XTerm, File Roller and the Home Folder.  Is this possible? Does there exist a free good molecule / atom simulation software? I'm looking for a software or software package (for example C/C++) that can simulate a lot (say thousands at least) of molecules in action (ie. in movement or attached to say static walls).  I have found several but they seems to be either 'gas only', 'water only', or not really scientific (a lot of small balls dodging around moved by an unique formula). Waiting for a file to be created in C# Why "be king", not "be a king"? I've heard people say "be king" (as in "I can't wait to be king") in movies and TV. Why don't they say "be a king"? Which is correct? Repeating an equation including its content and number I would like to re-use equations with the same content and number. I know that the thmtools package has a restatable environment to do this for environments (like in ), but I would also like to do this with a single equation that is only part of some environment.  I had a look at the following questions which only aim at repeating the equation number but typing the whole equation twice (the first three) or repeat the content of the equation without a number (the last one):         Based on the answers provided there and on the  I tried to create a macro \restatableeq for restable equations like this:  \documentclass{article}  \usepackage{amsmath}  \newcommand{\restatableeq}[3]{\label{#3}#2\xdef#1{\unexpanded#2\unexpanded\tag{\unexpanded\ref{#3}}}}  \begin{document}  \begin{eqnarray} \restatableeq{\eqone}{This &amp; is &amp; eqation 1}{eq1}\\ Another &amp; simple &amp; equation \end{eqnarray}  \begin{eqnarray} One &amp; more &amp; equation\\ \restatableeq{\eqtwo}{This &amp; is &amp; eqation 2}{eq2} \end{eqnarray}  Here, we use (\ref{eq1}) and (\ref{eq2}) again: \begin{eqnarray*} \eqone\\ \eqtwo \end{eqnarray*}  \end{document}   Unfortunately, it does not work and yields:  ! Missing { inserted. &lt;to be read again&gt;                    T l.10 ...ableeq{\eqone}{This &amp; is &amp; eqation 1}{eq1}                                                   \\ ?   My guess is that the &amp; symbols are not treated as intended but I may well be wrong there.  How can I define a command like \restatableeq that allows me to re-use equations with the same content and number in a setting like in this example (and give it a label such that I can still use \ref as usual in addition to that)? Word 2010 Number of pages without first page I show the number of pages as 1 / 4, with 4 being the total number of pages. But I do not want to count the first page.  Important: I know how to do it for the current page number (Starting at ..), I mean the total number of pages.  So if the document has one cover page + 3 pages, I want to show it as 1/3, 2/3 ..., not as 1/4. It's been more than a month since I have started using . It has these users with user names in the format of "user-random number". I have observed them in some of the stack activities, most of the time asking questions.   Does the moderators create them for their own purpose. If yes what purpose do they serve?   I mean a user is free to have any user name. But it's just a hunch that such users are actually moderators. I may be wrong; just need some clarification. Standalone python app that uses qgis.core without installing qgis