Why does Git not store file deltas?
Is the git storage model wasteful?
In the past month, I've been really busy with the university and stuff, and I don't sleep as much as I used to. I usually sleep 4-5 hours a night.  I haven't been doing that extensively ( I always kept a good sleeping routine), but can the lack of sleep affect my health on the long term ? Is this an equivalent formulation of "surjective" resp. "epimorphism"? Best vehicle for each stage in Hill Climb Racing In Hill Climb Racing we have several vehicles and several stages.  Different vehicles have different performances on the same stage, and I'd like to know what are the best combinations to maximize distance in each stage.    Also, what is the best combination of a vehicle and a stage to get lots of coins? What's the batched Refactor Fields tool "field mapping" syntax in QGIS? In QGIS, there is this nice tool "Refactor Fields" in the Processing Toolbox :    Using it on a single layer is fairly straightforward.  However, when you plan on using it in a batch mode, one can see the "Fields mapping" textbox. I'm looking for an example of the syntax to be used there.  I haven't found any specific documentation yet. Is it true that quantum mechanics technically allows anything to happen? Maybe this is a silly question (I think it is), but it's a question I'm arguing with some of my friends for a long time.  The ultimate question is: Is everything (in our Universe) possible ?  I've read some books (Penrose, Hawking, Greene, etc.) where it was clearly stated several times that quantum mechanics allows any situation to happen (e.g. everything is possible) - even with absurdly tiny probabilities?  Does this mean only physically possible - or "ultimate" possible ?  For example (I know this example seems really absurd, but I'm saying this so you get the idea) what my friends clame it is possible:   If I ask my friend(s): "Is it possible there is a Sun-sized star in my pocket right now?" They will respond: "Yes, there is very very tiny possibility this can be true!" Etc. From yesterday, openweather extention on the top panel does not show the weather. Its shows "Please wait Loading".  I tried to find the solution. There was a post of creating account on openweather website and use API id. I found that it is a subscription base plan. There was a free plan which allows 60 calls free for weather data.  I thought that the extention is open source. And may be I deleted any package that is required to work the extention so I reinstall the OS. But there is no difference of doing that.    What could possibly go wrong any guidance? Self-Contained Proof that $\sum\limits_{n=1}^{\infty} \frac1{n^p}$ Converges for $p > 1$ To prove the convergence of the p-series   $$\sum_{n=1}^{\infty} \frac1{n^p}$$  for $p &gt; 1$, one typically appeals to either the Integral Test or the Cauchy Condensation Test.  I am wondering if there is a self-contained proof that this series converges which does not rely on either test.    I suspect that any proof would have to use the ideas behind one of these two tests. pattern of moving electrons in wire under AC Cant find my harddrives in ubuntu installation? Two different solutions to integral I think it would be super if, in my LaTeX editor, I could click on the name of package...  \usepackage{blob}   ... and the corresponding style file, blob.sty, would be opened.  Do any LaTeX editors have this feature? I mainly use Aquamacs/AucTeX myself, but am interested in other editors too. I reckon it would be mildly challenging to implement, because blob.sty might be    in the current working directory,  in the system texmf directory, or  in the user's texmf directory. 74190 counter problem So, I got my 74190 counter shows number like this  9-8-7-6-5-4-3-2-1-0-5-4-3-2-1-0-5-4-3-2-1-0-5-4-3-2-1-0 and so on.  My questions:   What can I do to change the output count down into 5-4-3-2-1-0-5-4-3-2-1-0 and so on? When it changes 0 into 5 it moves so fast. How could I fix this one? I have a SRD-12VDC-SL-C relay with this configuration:  And I want to trigger it with PIR Motion Sensor Detector Module HC-SR501  The problem with direct connection to PIR is, when I connect PIR with 12v DC the Relay remains always ON, i.e. trigger from PIR does not switch it off. And when I connect it via 5V supply the Relay remains always OFF. The trigger output of PIR is 3.3V how can I rectify this problem? by adding some resistor/FETs, or something else. Edit: The voltage at Relay-In(Green) is 10.5V and the relay is OFF it need to go below 9V in order to switch the Relay ON. When I connect it to PIR trigger it goes down to 2.7V (Thus Switching ON the relay, below 9V). And when the PIR trigger of 3.3V comes it goes up to 7.2V but because it is still below 9V) Relay does not switch. Calling Table with custom iterator How to reduce the fan noise and how to increase battery life? I have a brand new Sony Vaio S series laptop.() It came factory installed with Windows 7 professional Edition 64bit. Runs Intel core i5, 500 GB HDD , 4GB Ram. First I installed ubuntu 11.10 64 bit along side Windows to dual boot. Later,since the problem did not solve, I installed ubuntu 12.04 64bit along side Windows to dual boot. However the problem keeps annoying me.  Problem: When running ubuntu 11.10/12.04, the battery lasts only about 1.5 hours. The Fan runs loud and continuously. And there is a lot of heat generated. System monitor shows less than 5% CPU used. My laptop enjoys hybrid graphic and I tried turning off ADM graphic card and keep Intel graphic card on. However I can not get the Fan noise or heat to go away and consequently the battery drain continues. BTW, in windows, the laptop gives 4-5 hours of battery power, Fan is silent and there is no heat problem. Any ideas on how to reduce the fan noise and how to increase battery life in ubuntu 11.10/12.04? How does ssh run a command? I'm using Bash on both client and server. When running a command over SSH:   ssh &lt;host&gt; 'declare' gives a list of shell variables. ssh &lt;host&gt; 'mount' gives a list of mountpoints.   However, declare is a Bash builtin, while mount is an external command. How does SSH know which to run if there is a shell builtin and an external command with the same name on the server? What does a "< <(...)" redirection mean? I've seen that rvm (ruby version manager) is installed using the following command:  bash &lt; &lt;(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer )   So as I understand we get the script content and pass it to the bash (I believe &lt; &lt; and &lt;&lt; is the same thing?) I am interested in the &lt; &lt; part, found following description on the net:     &lt;&lt; token    Means use the current input stream as STDIN for the program until token is seen.    This is somehow not clear for me, can someone make an example or explain it in more simple way? Rectifiability of a curve Let $f$ be a function defined on $[0,1]$ by   $$f(x) = { 0, \text{ if } x = 0} $$ $$f(x) = { x \sin \frac 1 x , \text{ if } 0 &lt; x \leq 1} $$  Prove that the curve $\{(x, f(x)) : x \in [0,1]\}$ is not rectifiable.   I'm not sure how to approach this. The general idea seems logical, we're proving that the length of the curve is infinite, but the method seems difficult to find. How can the pixel values of a raster image be extracted under a polygon fishnet? I have a single band raster image of 30m by 30m resolution. I have already created a polygon fishnet (grid) of 300m by 300m with point labels over that. How can I extract the mean pixel value of the raster image overlaying each feature in the fishnet grid? Is it possible with Arcgis?  Please inform me. A maximal ideal among those avoiding a multiplicative set is prime Let $S$ be a multiplicatively closed subset of a ring $R$, and let $I$ be an ideal of $R$ which is maximal among ideals disjoint from $S$. Show that $I$ is prime. If $R$ is an integral domain, explain briefly how one may construct a field $F$ together with a ring homomorphism $R\to F$. Deduce that if $R$ is an arbitrary ring, $I$ an ideal of $R$, and $S$ a multiplicatively closed subset disjoint from $I$, then there exists a ring homomorphism $f\colon R\to F$, where $F$ is a field, such that $f(x)=0$ for all $x\in I$ and $f(y)\neq 0$ for all $y\in S$.   [You may assume that if $T$ is a multiplicatively closed subset of a ring, and $0\notin T$, then there exists an ideal which is maximal among ideals disjoint from $T$.]  Here is a question I need to answer. For the first part I can show if $x, y$ are not in $I$ then nor does $xy$. The second part is just the field of fractions.   For the third part, I think I need to find an ideal $J$ containing $I$ such $J$ is prime, so that $R/J$ is an integral domain, and use the second part. To find $J$ prime, I think as suggested by the hint, I should go for a maximal ideal disjoint from $S$ containing $I$, but how can I do that?