I recall reading this story when I was much younger, in Spanish, and I think it was some sort of adaptation/translation.  At the time I thought it was great.  Later on, upon reading Mr. Bradbury's Martian Chronicles, I remembered it because of the similarity to his stories.  In the Spanish version I remember, either the human expedition/invasion to/of Mars (or the Martian expedition/invasion to/of Earth) have to be cancelled because of bureaucratic lack of funding.  Note: I am looking for the original story, NOT the Spanish translation/adaptation.  Thanks!
I'm trying to find a story for my father, from the 70s or earlier  Earth is at war with aliens (possibly Martians) and was unable to effectively fight back as the aliens had planetary (or at least city-protecting) force fields through which no bombardment was possible.  Earth eventually wins through invention of a device that allows them to teleport weapons (nukes?) under the force fields.  originally believed to be one of Harry Harrison's 'One step from earth' shorts, but this is not the case.  Thanks in advance for any help here!
I have a pretty simple table that needs to span multiple pages. This seems like a job for either the / package or the  package.   The voting on the answers to this  suggest that longtable is the preferred package, yet xtab is much newer and has been revised since that question was asked.  What are the differences between xtab and longtable and when is one preferable to the other? Cannot install Ubuntu in VirtualBox due to "this kernel requires an x86-64 CPU, but only detects an i686 CPU, unable to boot" error General integral to find resistance My question is: is there a simple and truly general equation for the resistance between two electrical equipotential surfaces?.  Obviously, if so, what is it, and if not, why?  It would be very difficult to solve, granted, but I just want to see a calculus equation that is fully descriptive.  I have two frameworks under which this could be entertained, I'll write those out and then explain the motivation.  To start with, we need propose that the volume separating the two surfaces has a volumetric resistivity, $\rho$ in units of $(\Omega m)$.  Single Volume Framework  We can limit the discussion to a defined volume, then the surfaces reside in that volume or on the surface of it.  This volume may have a constant resistivity $\rho$ while everywhere outside the volume is completely electrically insulating.  Infinite Volume Framework  An alternative to the above approach that might make the task more or less difficult would be to replace a constant resistivity with a spatial dependence $\rho(\vec{r})$ and no longer require a boundary condition.  In that case we only have 3 mathematical inputs to the problem, which is the resistivity defined for all $\vec{r}$ and a definition of the two surfaces, $S_1$ and $S_2$.  Known Algebraic Analogs  The  that I find insufficient is:  $$R = \rho \frac{\ell}{A}$$  Where $l$ is the length of the restive material that is any shape which has translation symmetry over that length, and $A$ is the cross-sectional area.  Obviously, this is a rather simple equation that won't apply to more complicated geometry.  Even more  seem to give equations that fall short of what I'm asking.  For example:  $$R = \rho \int_0^l \frac{1}{A(x)} dx$$  I think it's obvious that an equation such as this is built upon a myriad of assumptions.  For a thought experiment, imagine that the area starts out as very small and then pans out to very large quickly.  Well, accounting for the larger area in the above sense underestimates the resistance, because the charge has to diffuse out perpendicular to the average direction of flow as well as parallel to it.  I have some reasons to suspect this might actually be rather difficult.  A big reason is that all the approaches I'm familiar with require the flow paths to be established beforehand, which can't be done for what I'm asking.  So maybe this will result in two interconnected calculus equations.  Motivation  I had an interest in , and it occurred to me that I can't quickly and simply write down the equation for resistance between two points.  The unique thing about Squishy Circuits is that it calls for two types of dough, one that conducts and one that is mostly insulating.  However, the recipes aren't perfect and because of that, the young children who play with these circuits regularly encounter the limits of conductor and insulator definitions.  If you make your conductor dough too long and/or too thin, you will encounter dimming of the light you connect with it.  Similarly, a thin insulator layer will lead to a lot of leakage current which also dims the light. How to easily and completely disable/enable WLAN (so it cannot be turned on again while travelling)? Without going into specifics of why I might like to do this, or whether this is a good idea or not, I would like to know how I can disable use of wireless networking on my MacBook Air, either via removal of software or drivers or similar, such that the machine is unable to connect to a WIFI network in any way without I undo those changes.  The intention is for the machine to be unable to communicate wirelessly when out of the house, and for those changes to not be easily reverted until I return (for example requiring some piece of external storage that does not travel with me and which contains copies of whatever I have removed). How can I easily remove and then re-allow WIFI access (without losing my stored profiles/passwords or disturbing anything else)? Is it possible to simply copy a certain app or plugin to an external drive, delete it from my laptop, and later copy it back, again having everything as it was before?  One year later I have been happily using Daniel Lawson's solution below for quite some time now. I have created two applications with automator, one that deletes the .kext, one that restores it from an USB stick. First, copy /System/Library/Extensions/IO80211Family.kext to a USB stick and leave that stick at home. Open Automator, select to create an &quot;Application&quot;, then choose &quot;Utilities&quot; from the &quot;Library&quot;, then &quot;Execute Shell Script&quot;. (I'm translating this from my German menus, so the exact names may differ.) For the &quot;Disconnector&quot; app, enter the following into the text area of the &quot;Execute Shell Script&quot; event: echo YOUR_ADMIN_PASSWORD | sudo -S rm -rf /System/Library/Extensions/IO80211Family.kext  Replace &quot;YOUR_ADMIN_PASSWORD&quot; by your admin password. Then save the app and drag its icon to the Dock. Now, when you are sure you want to be free of all online distractions, click the app icon, and the IO80211Family.kext is gone. Just restart your laptop and you can no longer connect to WLAN:  For the &quot;Reconnector&quot; app, enter the following into the text area in Automator: echo YOUR_ADMIN_PASSWORD | sudo -S cp -r /Volumes/NAME_OF_YOUR_USB_STICK/IO80211Family.kext /System/Library/Extensions/  Replace &quot;YOUR_ADMIN_PASSWORD&quot; by your admin password and &quot;NAME_OF_YOUR_USB_STICK&quot; by the name of your USB stick. Save the app etc. Now when you return home, insert the USB stick that carries the IO80211Family.kext into your laptop, click the Reconnector app icon and then restart your laptop. Now you can connect to WLAN again. Note. There are some security issues invovled when you echo your admin password, because by that it is written to the shell history and can be found there. I don't care, but you might, depending on your circumstances. Piping for loop output prevents local variable modification I'm trying to write a simple bash function that takes, as its arguments, a number of files and/or directories. It should:   Fully qualify the filenames. Sort them. Remove duplicates. Print all that actually exist. Return the number of non-existent files.   I have a script that almost does what I want, but falls down on the sorting. The return value of the script as it stands is correct, but the output is not (unsorted and duplicates). If I uncomment the | sort -u statement as indicated, the output is correct but the return value is always 0.  N.B. Simpler solutions to solve the problem are welcome but the question is really about why is this occurring in the code I have. That is, why does adding the pipe seemingly stop the script incrementing the variable r?  Here's the script:  function uniqfile {     local r=0       for arg in "$@"     do           readlink -e "$arg" || (( ++r ))      done #| sort -u    ## remove that comment      return $r } GLR Test for 2 samples from exponential distributions How do you Programmatically Download a Webpage in Java Do computer viruses affect all user accounts on a computer? Do computer viruses affect all user accounts on a computer?  IF a virus affects a local user will that effect administrator account and vise-versa? Finding a basis for a certain vector space of periodic polynomials I am having a little bit of trouble solving an homework question.  I found that $S={ p(x) \in R_4[x]} \big| p(x)=p(x-1) $ is a vector space.  Now I need to find some set, K that holds ${span(k)=S}$  My idea was to substitute: $ a+bx+cx^{2}+dx^{3}+ex^{4}=a+b(x-1)+c(x-1)^{2}+d(x-1)^{3}+e(x-1)^{4}$  But here I get something that seems a little bit weird, I'd like to look if I have any mistakes that I did not notice. and if I had mistakes, how to make my answer right. I calculated the right side of the equation and I got to  :  $a+b(x-1)+c(x-1)^{2}+d(x-1)^{3}+e(x-1)^{4}=a+bx-b+cx^{2}-2cx+c+dx^{3}-3dx^{2}+3dx-d+ex^{4}-4ex^{3}+6ex^{2}-4ex+e= (a-b+c-d+e)+(b-2c+3d-4e)x+(c-3d+6e)x^{2}+(d-4e)x^{3}+ex^{4}  $  From here, $ (a-b+c-d+e)+(b-2c+3d-4e)x+(c-3d+6e)x^{2}+(d-4e)x^{3}+ex^{4}=a+b(x-1)+c(x-1)^{2}+d(x-1)^{3}+e(x-1)^{4}\Rightarrow $  $(-b+c-d+e)+(-2c+3d-4e)x+(-3d+6e)x^{2}+(d-4e)x^{3}=0+0x+0x^{2}+0x^{3}+0x^{4}$  And the solution to this equation is only whan $a=b=c=d=e=0$.  I think that I am maybe not in the right direction. Do you have any Idea how to find a set $K\Rightarrow span(K)=S$ ?  Thanks in advance. I am fairly new to Unity3D experience , but I have a very good knowledge of Java and Android development. I am really confused that if Java is at all needed for developing android applications? I read somewhere in Unity documentation that adding behaviour to objects in Unity requires use of scripts, and that unity only supports C# , .Net , and Boo scripts. Is there no use of Java at all? I've seen the identity $\displaystyle \sum_{i \mathop = 0}^n \binom n i^2 = \binom {2 n} n$ used here recently.  I checked for proofs here   I couldn't have figured out the combinatorial proof by myself, and the inductive proof assumes you already know the answer...  So my question is : do you know how to prove directly through computation that $\displaystyle \sum_{i \mathop = 0}^n \binom n i^2 = \binom {2 n} n$ ? Gauss's Lemma for polynomials claims that a non-constant polynomial in $\mathbb{Z}[X]$ is irreducible in $\mathbb{Z}[X]$ if and only if it is both irreducible in $\mathbb{Q}[X]$ and primitive in $\mathbb{Z}[X]$.   I wonder if this holds for multivariable case.      Is it true that a non-constant polynomial in $\mathbb{Z}[X_1,\dots,X_n]$ is irreducible in $\mathbb{Z}[X_1,\dots,X_n]$ if and only if it is both irreducible in $\mathbb{Q}[X_1,\dots,X_n]$ and primitive in $\mathbb{Z}[X_1,\dots,X_n]$?    Thank you for your help. How to configure Jaybird with hibernate What is the origin of elements heavier than iron? In all the discussions about how the heavy elements in the universe are forged in the guts of stars and especially during a star's death, I usually hear that once the star begins fusing lighter atoms to produce iron (Fe) that's the end of the star's life and the whole system collapses onto itself; and based on how massive the star was initially, it has different outcome - like a white dwarf, a neutron star or a black hole. I have rarely heard a detailed explanation of how the elements heavier than iron are produced. I would appreciate a convincing explanation of this process. I saw a video of Johann Cruyff , isn't that against the rules? Just a curiosity. I just saw a video where pi was being calculated by the series  $$1-(1/3)+(1/5)-(1/7)+...$$  My question is how can $\pi$ be irrational if we can calculate it using rational numbers? Was Daenerys actually trying to hatch the eggs? I was reading @Aegon' s response   and I realized that I've never been clear on whether Dani was intentional in her pyre building to do blood magic and wake the dragons, or if she was just grieving Drogo and killing Mirri and her statement about "only death can pay for life" was a slap in the Maegi's face, since in the end she sacrificed her unborn child for the husk of Drogo.    I know she had tried baking the eggs previously and had felt like they could hatch then, but was clearly disappointed and chastised herself for foolishness when they did not. I don't recall inner monologue or statements after that where she said, "ya know what I should have done..."   I guess what I'm asking is whether there is evidence outside her statement to the Maegi that she was intentional in her blood magic rite or if the miracle was a happy accident? Why can I not access a file named `-` when quoting? I have a file called -.  I want to display its contents.  One way is to do  cat ./-   since cat - reads from standard input. However, why are cat "-" and cat '-' also interpreted by the shell as cat -? Converting MultiLinestring to Linestring with PostGIS I have a multiline string and want to convert it to a linestring in order to use some functions that only work with linestrings. I used ST_Dump() and got a collection of my geometries. If I merge them back together, I still get the multilinestring. Should I get the Npoints and combine them together or something, in order to end up with a simple linestring? ST_LineMerge() also does not work on my multilinestring, it returns the same. my example,  MULTILINESTRING((-3.16420835153456 55.9269166007097,-3.164222 55.926918),(-3.1642070167833 55.9269296196706,-3.16421351659546 55.9268662214904),(-3.16421351659546 55.9268662214904,-3.16421636372824 55.9268384509897),(-3.16421636372824 55.9268384509897,-3.16422182573761 55.9267851753802),(-3.16422182573761 55.9267851753802,-3.16422870102352 55.926718114886),(-3.16422870102352 55.926718114886,-3.16423309121073 55.926675293667),(-3.16423309121073 55.926675293667,-3.16423565148822 55.9266503211093),(-3.16423565148822 55.9266503211093,-3.16424103159897 55.9265978443265),(-3.16424103159897 55.9265978443265,-3.16424680776317 55.9265415044985),(-3.16424680776317 55.9265415044985,-3.16425267254583 55.9264843002995),(-3.16425267254583 55.9264843002995,-3.16425541048045 55.9264575949012),(-3.16425541048045 55.9264575949012,-3.16426111146586 55.9264019883556),(-3.16426111146586 55.9264019883556,-3.1642667032531 55.9263474469124),(-3.1642667032531 55.9263474469124,-3.16426957768543 55.9263194101362),(-3.16426957768543 55.9263194101362,-3.16427488261739 55.9262676666359),(-3.16427488261739 55.9262676666359,-3.16428009893088 55.9262167875066),(-3.16428009893088 55.9262167875066,-3.164282741107 55.9261910161221),(-3.1642875546472 55.9261440655823,-3.164282741107 55.9261910161221),(-3.1642875546472 55.9261440655823,-3.16429466890915 55.9260746741522),(-3.16429466890915 55.9260746741522,-3.16430092974527 55.9260136069079),(-3.16430092974527 55.9260136069079,-3.16430822838418 55.9259424170929),(-3.16430822838418 55.9259424170929,-3.16431547242401 55.925871759829),(-3.16431547242401 55.925871759829,-3.16431448732505 55.9258328901507),(-3.16431770120536 55.9257327846001,-3.16431547242401 55.925871759829),(-3.164339 55.925777,-3.16431770120536 55.9257327846001)) The inequality is homogeneous, but I am not sure if that helps. Also, I was thinking about considering a concave function and apply Jensen or Karamata on LHS.