After reading an article on Schrodinger's Cat, it seems that if we take the environment as an observer, that superposition cannot occur because all atomic and subatomic entities would be observed all the time. Thus, something like quantum entanglement cannot occur. So if superposition cannot occur, why is superposition (and by extension quantum entanglement) still part of quantum mechanics?  Updated: In the question , the notion of observer is replaced by measurement. In this context, my question would be: if the system (cat) is constantly being measured by the environment (the observer is watching the cat), how can superposition (the cat is in multiple states; i.e., alive and dead) exist in quantum mechanics?  For example, if a photon passes by a heavy particle and splits into an electron and positron, the splitting process is a measurement of the electron and positron to make sure the total spin is 0. I understand the argument that we might not know which has +1/2 and which has -1/2, but the observation/measurement had to be done to make sure we didn't have 3/4 total spin.
I don't understand how quantum mechanics (and therefore also quantum computers) can work  given that while we work with quantum states, particles that this quantum state consist of cannot be observed, which is the most fundamental requirement.  If I am not mistaken, by "observed" we mean interaction with any other particle (photon, gluon, electron or whatever else). So my very important questions:   Aren't the particles this quantum state consists of interacting with each other? Why doesn't that cause the state to collapse? Aren't all particles in the universe interacting with Higgs field and gravitons etc? Why doesn't that cause every quantum state to collapse?   I feel there is something very fundamental in quantum mechanics that I am not aware of, hence I would be very pleased to have these questions answered.
Which experiments prove atomic theory?  Sub-atomic theories:   atoms have: nuclei; electrons; protons; and neutrons. That the number of electrons atoms have determines their relationship with other atoms.   That the atom is the smallest elemental unit of matter - that we can't continue to divide atoms into anything smaller and have them retain the characteristics of the parent element. That everything is made of atoms.     These sub-theories might spur more thoughts of individual experiments that prove individual sub-atomic theories (my guess is more was able to be proven after more experiments followed). How to Toggle Selected Objects Visibility with H shortcut as in Maya I want to be able to toggle the visibility of selected objects with a shortcut (H) the way you can do in Maya and XSI, shown in the GIF. I'm guessing scrippting is needed. I've tried to do it my self but I'm new to Python and Blender and as soon as the objects are hidden they seem to no longer be in a selection state/list. Eg if I manually select the hidden object/s in the Outliner and try to print the selected object to the console, none seem to be selected. Is this possible to do with the current state of Blender 2.8? Are users' reputation scores on the home page supposed to stand out that much now? It seems a couple minutes ago, a change was applied to the styling of the homepage, with users' rep scores now being much darker (and standing out more):        Compare with the former light grey colouring (image courtesy of ):        Is this intentional? If so, why? It highlights something that's not really relevant, in my opinion. chrome disable or change keyboard shortcut ctrl+shift+c developer tools console? How can I disable the Keyboard Shortcut ctrl+shift+c in Google Chrome to bring up the Developer Tools console?  I find myself trying to copy+paste content from the browser and mistakenly typing ctrl+shift+c when I really want to do ctrl+c instead.  How can I disable the current keyboard binding or change ctrl+shift+c to do the same as ctrl+c in Google Chrome? What I want is to create a bootable pen drive that shows GRUB menu and I can select any of the several bootable systems from there to install/run. I have several ISO images that I want to install in the USB like Ubuntu, Fedora, System Rescue CD, Windows XP and Windows 7 (The windows versions are optional, mostly am looking for a multi installer for Linux distros, specially Ubuntu version)  The default Startup Disk Creator only works with Linux Images and only 1 at a time (At least for the mean time. If it allows more systems and multiple ISOs it would be awesome)  What method exists that I can use step by step to create a bootable USB Drive with multiple images than can be booted from the USB and selected from GRUB. It must support Windows Images and Linux Images.  Alternatively, is there also a way to have multiple versions of the Ubuntu installation ISO on same USB Drive, such as, when booting from it, I get to choose what Ubuntu version and architecture to install, for example:     BOOT MENU   Ubuntu 12.04 32 Bit   Ubuntu 12.04 64 Bit   Ubuntu 12.10 32 Bit   Ubuntu 12.10 64 Bit   UPDATE: Wanted to add that the English version for the post mentioned by daithib8 is here: My Bash Prompt is currently setting the xterm titlebar using the following sequence:  PS1='\033]0;\u@\h&gt;\w\007'   Is there an easy way to display the current command in the titlebar. For example, if I am tailing a file using tail -f foo.log, I want my titlebar to say tail -f foo.log. I'm looking for the fastest way to determine if a long value is a perfect square (i.e. its square root is another integer):    I've done it the easy way, by using the built-in  function, but I'm wondering if there is a way to do it faster by restricting yourself to integer-only domain. Maintaining a lookup table is impractical (since there are about 231.5 integers whose square is less than 263).   Here is the very simple and straightforward way I'm doing it now:  public final static boolean isPerfectSquare(long n) {   if (n &lt; 0)     return false;    long tst = (long)(Math.sqrt(n) + 0.5);   return tst*tst == n; }   Note: I'm using this function in many  problems.  So no one else will ever have to maintain this code.  And this kind of micro-optimization could actually make a difference, since part of the challenge is to do every algorithm in less than a minute, and this function will need to be called millions of times in some problems.    I've tried the different solutions to the problem:   After exhaustive testing, I found that adding 0.5 to the result of Math.sqrt() is not necessary, at least not on my machine. The  was faster, but it gave incorrect results for n >= 410881.  However, as suggested by , we can use the FISR hack for n &lt; 410881. Newton's method was a good bit slower than Math.sqrt().  This is probably because Math.sqrt() uses something similar to Newton's Method, but implemented in the hardware so it's much faster than in Java.  Also, Newton's Method still required use of doubles. A modified Newton's method, which used a few tricks so that only integer math was involved, required some hacks to avoid overflow (I want this function to work with all positive 64-bit signed integers), and it was still slower than Math.sqrt(). Binary chop was even slower.  This makes sense because the binary chop will on average require 16 passes to find the square root of a 64-bit number. According to John's tests, using or statements is faster in C++ than using a switch, but in Java and C# there appears to be no difference between or and switch. I also tried making a lookup table (as a private static array of 64 boolean values).  Then instead of either switch or or statement, I would just say if(lookup[(int)(n&amp;0x3F)]) { test } else return false;.  To my surprise, this was (just slightly) slower. This is because . How to type a circumflex over a greek letter in text mode? prints out a lot of very detailed protocol statistics like number of TCP reset messages received or number of ICMP "echo request" messages sent or number of packets dropped because of a missing route.  When in Linux netstat is considered deprecated at nowadays, then is there an alternative?  Statistics provided by ss -s are superficial compared to the ones provided by netstat. Why does no physical energy-momentum tensor exist for the gravitational field? How do I read and parse an XML file in C#? What are the system requirements for each flavour of Ubuntu Desktop? I'm thinking about installing Ubuntu Desktop, but I don't know what flavor is the best for my system. What are the minimum and recommended hardware requirements? What kind of CPU? How much memory? Should I have Hardware Acceleration? What flavor should I use?  This is an attempt of a canonical answer. My answers have the &quot;official  requirements&quot;, the recommended are a mix of official sources and opinion based (along with the answer it's told the source). You can comment or edit if you feel that the information is obsolete or incomplete. It is a good rule of thumb that any system capable of running Windows Vista, 7, 8, x86 (Intel) OS X will almost always be a lot faster with any Ubuntu flavor even if they are lower-spec than described below. Why is list initialization (using curly braces) better than the alternatives? What is a simple way to create a binary relation symbol on top of another? What is a simple way to have \ll on top of \gg with equal size and vertically center aligned and have them work as a binary relation symbol like \lessgtr? The commands \underset and \overset cannot be used because they do not treat the two symbols equally, and they do not vertically center. Can I launch a graphical program on another user's desktop as root? Following are other questions which I think I need to know:   From a non X Session? (meaning root isn't logged into X) If multiple people were logged in on X, could I auto-detect who was on which screen, and thus programmatically detect which screen I need to launch the app on? Can I launch the app as the user? ( ok I'm 99.999% sure this is a yes ) Can I detect if users of group X are logged in to X? Graphing the amount of time a function takes I'd never heard of anycast until a few seconds ago when I read "".  The wikipedia "" article on it is quite formal and doesn't really evoke a mental picture of how it would be used.  Can someone explain in a few informal sentences what "anycast" is, how you configure it (just in a general sense), and what its benefits are (what does it make easier)? I will try to be as explanatory as possible with my question. Please also note that I have done my share of googling and I am looking for simple language preferable with some example so that I can get some insight in this subject.  My question is what is so special about $c$? Why only $c$. Its like chicken and egg puzzle for me. Does Einstein reached to $c$ observing light or does he got to light using some number which turned out equal to $c$.   Why is $c$ not relative. If something has zero rest mass like a photon why they only travel at $c$ in vacuum and not with $c+1$ or $c-1$? Prove or disprove that $f(x) = \sin x/x$ is uniformly continuous over the interval $(0,1)$? I am thinking of $\lim_{x \to 0} \ {f(x)} = 1$ but I am confused as $x=0$ is not in the domain and also I want to write an $\epsilon$-$\delta$ proof. So any help is much appreciated!  Thanks! Which infinity is meant in limits? For example, when we write $\lim_{x\rightarrow \infty} f(x)$ - which infinity is meant and why? Countable? If uncountable - which and why?