Current theories about Universe dimensions and age put them - respectively - at about 90 G light-years wide and 13.8 G years old. To avoid implying that matter travelled faster than light, theories state that - sometime after 'time 0' - space wildy expanded "by itself", so that matter ended up enormously scattered in spite of having moved very little in comparison.  This - possibly as many other concepts in modern physics which work perfectly but remain un-imaginable - SEEMS to me to imply that:   1) No matter how big the Universe is, and what tools we will have available, it will never be possible to "see" anything coming from farther than 13.8 G light years  (nothing travels faster than light); if this happened, the age of the Universe would be updated;  2) Looking very far away in one particular direction, we might be actually looking at ... ourselves, i.e. to the matter now composing our galaxy when it was still there, before being "shooted" where it is now by the expansion of space, and be reached by its own light !  3) The expansion of space creates/created enormous "gaps" amongst matter, where absolutely nothing is/was present, until waves of all sorts (gravitational &amp; electromagnetic) reach and start moving through it;  4) The fact that we are now receiving light 13.5 G years old  from far-away galaxies scattered in every direction, means that we now are at least 13.5 light years from the current "borders" of the universe. Provided - of course -  that a "centrifugal" expansion of  the Universe still makes any sense, with theories which no longer have anything in common with ... common sense.   Most of them seem very odd conclusions. Am I wrong on all the line ?
The observable universe is approximately 13.7 billion years old. But yet it is 80 billion light years across. Isn't this a contradiction?
How does gravity work underground? Would the effect of gravity on me change if I were to dig a very deep hole and stand in it? If so, how would it change? Am I more likely to be pulled downwards, or pulled towards the edges of the hole? If there would be no change, why not? Remember a half-typed command while I check something I often find myself in the following position: I've started typing a long command at the bash prompt, but half-way through I find out I need to check something with another command. This is a problem when I'm at the console (no X), which is often the case, because then I only have the following unsatisfactory ways to do it, that I know of:    Hit ctrl+alt+F2 and log in on another virtual console, and find out what I wanted, then go back and continue  ctrl+a, type echo + space + enter, find out what I wanted, press ↑ until I find my command, ctrl+a, del x 5, ctrl+e, and continue  Highlight what I've typed so far with my mouse (if gpm is running, which it usually is), press ctrl+c to interrupt, find out what I wanted while being careful not to use my mouse to highlight stuff, then press middle mouse button on a new prompt and continue  Pray to the command line gods that the half-written command will have no adverse effects but simply fail, and gingerly press enter, then find out what I wanted, press uparrow until I get my command back, and continue  Jump into my time machine, travel back in time and remind myself to start screen before starting to type command, travel back to the present, press ctrl+a c, find out what I wanted, press ctrl+a ctrl+a, and continue   So what I want to know is, is there some more elegant way of doing this? A sort of subshell-command or similar?  I'm most interested in methods that do not require any preparations or setup to work. Best way to encode list names in sharepoint 2013 rest url's? Pivot rows into multiple columns I have a SQL Server instance that has a linked server to an Oracle server. There is a table on the Oracle server called PersonOptions which contains the following data:  ╔══════════╦══════════╗ ║ PersonID ║ OptionID ║ ╠══════════╬══════════╣ ║        1 ║ A        ║ ║        1 ║ B        ║ ║        2 ║ C        ║ ║        3 ║ B        ║ ║        4 ║ A        ║ ║        4 ║ C        ║ ╚══════════╩══════════╝   I need to pivot that data so the results are:  ╔══════════╦═════════╦══════════╦══════════╗ ║ PersonID ║ OptionA ║ Option B ║ Option C ║ ╠══════════╬═════════╬══════════╬══════════╣ ║        1 ║       1 ║        1 ║          ║ ║        2 ║         ║          ║        1 ║ ║        3 ║         ║        1 ║          ║ ║        4 ║       1 ║          ║        1 ║ ╚══════════╩═════════╩══════════╩══════════╝   Any suggestions? C# Mono - Low Level Keyboard Hook I'm using code that I found on the .  The only problem is it uses external DLL calls that don't work in mono.  I was wondering if anyone knew of a way to accomplish the same thing as that code, but will run in both Windows using .net, and Linux using mono?  Edit:  Clarifying what I'm trying to do: I'm making a .  The program sits in the system tray and when the user presses the hot-key, it will pop up all the gadgets.  So the program doesn't have focus, so typically it won't catch any keystrokes, so I'm using the low-level keyboard hook and I hook the two keys that the user defines as the hot-keys.  But I'm using a Windows DLL call for that, which doesn't work in Linux using mono.  So I'm wondering if there's a way to do the same thing, but will run in Linux using mono? What is the status of pdfsync? The pdfsync homepage states that:     At the end of this summer (2007), pdfsync is slowly migrating to pdftex itself. We are working at giving pdftex all the pdfsync ability and more...   The pdfsync README file discourages people from using pdfsync:     pdfsync uses extremely sensible code. You should not use pdfsync on final documents because it can change the layout rather significantly.   From your knowledge and experience, what is the actual status of pdfsync?   Is it safe to use pdfsync? Is there an alternative for pdfsync that is built into pdftex? Is there a different tool for pdflatex that offers DVI-like functionality (forward and backward search)? Prove that polynomial of degree $4$ with real roots cannot have $\pm 1$ as coefficients (IITJEE) So I was going through  my 11th class package on Quadratic equations and I saw a question to prove that a polynomial of $4$th degree with all real roots cannot have $\pm 1$ as all its coefficients.   I tried proving it using calculus, by showing that at least one consecutive maxima  and minima will lie either above or below the x axis, but couldn't solve it using that.  I also tried using Descartes Rule of Signs but couldn't solve it with that too. Any help? Java date format conversion - getting wrong month What does "it" refer to in "it's raining"? Computing $ \int_0^\infty \frac{\log x}{\exp x} \ dx $ How can I change the color of a part of a TextView? I got some new hard discs and would like to set my PC up in the following way:   Ubuntu is currently installed on one drive I want to put Windows on a second drive I would like a third drive for shared content (music and stuff) that both OSes can access     What I need to know is what format should the content drive be?  How should I configure the drive order in my bios for GRUB to be boot manager and how to configure GRUB for multi-HDD booting? Inverse of a diagonal matrix plus a constant I am looking for an efficient solution for inverting a matrix of the following form:  $$D+aP$$   where $D$ is a (full-rank) diagonal matrix, $a$ is a constant, and $P$ is an all-ones matrix.   gives a solution to the special case where all diagonal entries of $D$ are the same.  The  formula is also capable of providing a solution to this problem by setting appropriate $u$ and $v$, but it loses efficiency ($O(n^3)$ time complexity to compute) at high dimension. I am hoping to get a result in the same form so the space and time complexity are both $O(n)$. Propane gas fireplace pilot won't light Reusable functions in jQuery callback How does the tester screwdriver work? How does the tester screwdriver work? If I put the tester screwdriver inside the "hot wire" of an electrical socket, it lits up if I press my finger against the metal cap on top of the screwdriver. This happens also if I stand on a surface of isolating material, such as wood. I read elsewhere that this happens due to stray capacitance formed by the "hot wire", the human body, and the ground. One has  $$ Z = R + \dfrac{1}{j \omega C}  $$  for the impedance, so if C  is high enough, the impedance should be close to r , the "effective resistance" of the formed circuit. Here I get lost; why r  is small enough to cause a current in the range of mA  even if I stand on an isolating surface?  So really what I am asking is how one may represent the system hot wire - screwdriver - human body - wooden floor - building - ground as an electrical circuit, and which parts of the physical system contribute to the resistance, capacitance (and inductance?) and in which proportion, even very approximately. Error message "sudo: unable to resolve host (none)" How do I summon a baby mob? In Minecraft Java Edition, one can summon baby zombies and drowned using the IsBaby NBT tag: /summon zombie X Y Z {IsBaby:1b}  Likewise, one can summon baby breedable mobs (Pigs, Cows, etc.) by giving them a negative Age NBT tag (the number of ticks until the mob grows up): /summon cow X Y Z {Age:-100000}  Since NBT is inaccessible from commands in Bedrock Edition, the above commands will not work there. How do I summon baby mobs in Minecraft Bedrock Edition? Example of a function such that $\varphi\left(\frac{x+y}{2}\right)\leq \frac{\varphi(x)+\varphi(y)}{2}$ but $\varphi$ is not convex Why exactly can't a single resistor be used for many parallel LEDs?