If is was to stand deep inside the center of a black hole and was to point a light gun straight up at the center of the event horizon, would the beam of light make it out of the black hole?
I have a couple of questions about light here, and sorry of they are silly..  So since anything that goes beyond the event horizon can't go out, so what if a light beam was pointed somewhere behind the event horizon to the outside, would light have a slower speed then get sucked back? and what if the light particles were somehow exactly on the event horizon, would the light stand still?  And why can't light stand still? why does it always move at that really high speed?
Ubuntu 14.04: very slow UI in Oracle VirtualBox Short summary: 14.04 is much slower than 12.04 even with more RAM assigned.  I'm using latest VirtualBox 4.3.10 on Mavericks 10.9.2. How can I make it faster? a two hour leave VS. two hours leave I couldn't get the difference between these?   give me a two hour leave  give me two hours leave    What is more, when it comes to using the latter, which one would you rather use? two hours' leave two hour leave The keyboard I am trying to create has a lot of Unicode and looks like this:   Being unsuccessful with the following tutorial:    (There are a few errors in the tutorial, and it uses imprecise language such as "Cutting" things instead of "Deleting" them, and it is formatted strangely)   I was wondering if anybody would be so kind to provide a better tutorial with step by step instructions? How can I efficiently generate a Set from a List structure? I have a bit of code where I've written a SOQL query that returns a list of SObject records, however I need a Set&lt;Id&gt; structure to pass to another method that I don't have control of (and thus can't change the method signature of).  How can I turn my returned List&lt;SObject&gt; into a Set&lt;Id&gt;? Is the best option just a for loop? What is the most efficient way to write the old-school:  StringBuilder sb = new StringBuilder(); if (strings.Count &gt; 0) {     foreach (string s in strings)     {         sb.Append(s + ", ");     }     sb.Remove(sb.Length - 2, 2); } return sb.ToString();   ...in LINQ? What is the difference between these two ways to calculate average velocity? Average velocity:  $$v_{\rm avg,1}=\frac{v_{\rm final}+v_{\rm initial}}{2}$$   and average velocity:   $$v_{\rm avg,2} =\frac{\rm total\;displacement}{\rm time \;taken}=\frac{\Delta x}{\Delta t} $$  What is the difference between them and when do we use them? Can someone identify this book, where children are bred for specific jobs? Things I remember about this book:   Every child was selected for a certain job/career; If twins were born, one was always killed; Seeing colors for the first time (describing the color of an apple); Seeing war and death and poverty.   Does anyone have any idea what this book might be? why arcane legacy steps to boot from USB with GPT and UEFI? To run the live AVG rescue "disk" on USB for Windows 10, how is it made to work with a GPT and UEFI system?  (Possible solution listed below.)  I enabled the boot menu so that pressing F12 will display a list to select from.  Also, I put everything USB at the top of the boot sequence and Windows and the HDD at the bottom.  However, I hadn't realized GPT and UEFI are so different from a BIOS.  Because the USB flash drive isn't compatible with GPT it's not being picked up?  This  was suggested:   Open the notebook and press quickly F2 to enter the BIOS. Under the MAIN menu, enable the F12 Boot Menu option. Under the BOOT menu, select Legacy boot and press F10 Save &amp; Exit. While the notebook is rebooting, press F2 again to enter the BIOS. Under the BOOT menu, select as your first boot option the USB HDD stick (your USB stick). Press F10 Save &amp; Exit.    Perhaps this will work, but what is the problem that prevents UEFI boot from registering the thumb drive?  Because it's using GPT and not an MBR?  I don't want to switch to legacy, but stay with UEFI.  The laptop: How do you transpose tensors? We transpose a matrix $A$ by replacing $A_{ij}$ with $A_{ji}$, for all $i$ and $j$.  However, in case $A$ has more than two dimensions (that is, it is a tensor), I don't know how to apply the transpose operation.   If A has dimensions $3\times 3 \times 8$, then what will replace $A_{ijk}$?  If $A$ has shape $3\times 3\times 8\times 8$, then what will replace $A_{ijkl}$? For example, on Debian or Ubuntu, which package has the /sbin/shutdown command in it? I want to read the source of that command (and possibly modify it to report notification on desktop) and I didn't know which package source to download. Black is Back! New update with Achievement shows black backgrounds with black text Update: This is fixed on version 1.0.43 as per the accepted answer below.  Already saw ,  and . They are old and seem to be about previous versions.  I just updated to the version 1.0.41 of the Android app that brings the new feature - Achievements. Sadly, I think the stress of World Cup has made you guys not do a good job with it. It's buggy.  When I open my Achievements panel and tap on any post, I get this:    After I get this, it persists throughout the rest of the app. For example, if I go to the feed and open another question, I get this too.  Detailed reproduction steps are available in AD7six's answer.  My Device: Samsung Galaxy SIII LTE GT-I9305 Android: Stock ROM 4.3 Jelly Bean  Other Devices: - Device model, Android version, Reported by - HTC Desire, 4.2.2, xd6_ - Huawei Ascend, 4.2, Manu343726 - LG Optimus F3, 4.1.2, Rocket Hazmat - LG Optimus G, 4.3, Canadian Luke - Samsung Galaxy Nexus (Sprint), 4.3, Chrono Kitsune - Samsung Galaxy Note II, 4.3, Katja Christiansen - Samsung Galaxy SII GT-I9100, 4.1.2, AD7six - Sharp SH837W, 4.1.2, timrau - Sony Xperia SP, 4.3, pepoluan - Sony Xperia Z1, 4.3, user2313067 - Unknown, 4.2.1, Deer Hunter Is it worth it to buy an FD-EOS adapter, or is it better to exchange a misbought lens? I recently bought a manual-focus (since manual doesn't bother me) . However, I didn't notice at the time of purchase that it was an FD lens. (I'm a hobbyist; I didn't know Canon had actually changed lens mounts at some point.)  On the one hand, I kind of want to experiment with this guy. And quality FD lenses are relatively cheap on the used market, so if the adapters were worth it, I could probably get more (and more varied) glass. On the other hand, everything I read about the FD-EOS adapters is highly contradictory. As in, some people swear by them, and others think they're outright tripe.  I am still within the exchange period, and can easily exchange this lens for this  that I'd been tossing up about buying anyway, as they are the same price.  Which would be the wiser choice? How many syllables are in the word 'hour'? Does the word 'hour' have 1 or 2 syllables? What is time, does it flow, and if so what defines its direction? Let $a$, $b$, and $c$ be complex numbers with $a\neq0$. Show that the solutions of $az^2+bz+c=0$ are $z_1,z_2=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$, just as they are in the case when $a$, $b$, and $c$ are real numbers. How to clear current “read-only” state on a USB flash drive I setup with Rufus? Three weeks ago I used  2.2 to install Windows 10 on my machine, and it has write-protected my flash drive. I’ve tried diskpart:  diskpart att disk clear readonly  clean create partition primary format fs=fat32 quick   And it kinda worked, it removed the image off the USB, but now it’s showing:  Current Read-only State : Yes Read-only  : No Boot Disk  : No Pagefile Disk  : No Hibernation File Disk  : No Crashdump Disk  : No Clustered Disk  : No   And I can’t format it or write on it.    The drive is a a Kingston DataTraveler G4 32GB model, without physical switches. How would I restore it back to normal (rw) state? One thing that made me curious while watching a football game on TV was the numbers that appear on the ground. For instance, there's a "1st &amp; 10" beside one team, but there was a "3rd &amp; 6" a few minutes prior (and I think it was beside the other team). What do these numbers mean? I did not create a swap partition during Ubuntu installation.  Later, I freed up some space and made a swap partition.  Now after each boot up, I am manually opening gparted to right-click the swap partition to turn on the 'swapon' option.  How can I automatically enable the swap partition at boot?  Also, if I had not created the swap partition, what are my other options? Let $X,Y,Z$ Banach spaces and $A:X\rightarrow Y$ and $B:Y\rightarrow Z$ linear maps with $B$ bounded and injective and $BA$ bounded. Prove that $A$ is bounded as well.   If I knew that $B(Y)$ is closed I'd have a bounded linear map $B^{-1}:B(Y)\rightarrow Y$ by the bounded inverse theorem. Therefore $A=B^{-1}BA$ is bounded. How to prove the claim if $B(Y)$ is not closed. Difference between spin and polarization of a photon I understand how one associates the spin of a quantum particle, e.g. of a photon, with intrinsic angular momentum. And in electromagnetism I have always understood the polarization of an EM wave as the oscillations of the E and M field, not necessarily being  aligned with the direction of propagation of the wave.     Questions:   But when one talks about the polarization of a photon in Quantum Mechanics, how does it really differ from its spin?  Are they somehow related and what's the physical idea behind photon polarization in contrast to photon-spin? Feel free to use mathematical reasonings as well if you see it fit!