Difference between: "it has rained / been raining for two hours"
What's the meaning of this present perfect sentence?
Is there a way to see questions with a certain tag from all Stack Exchange sites? For example, I see there are questions with the  tag on Stack Overflow, but there are also such questions on Super User, Unix/Linux, and other sites in the network.  Is there a way to follow a tag across all of the Stack Exchange sites, so that one can see the global activity of a topic without visiting all the sites separately? I would like to understand how Physicists think of space-time in the context of String Theory. I understand that there are $3$ large space dimensions, a time dimension, and $6$ or $7$ (or $22$) extra dimensions, and all these dimensions need to fit together in a way such that the extra dimensions are compactified (with a Calabi-Yau or $G_2$ structure).   My question, however is not about the possible $10$, $11$ or $26$ dimensional manifolds that may be possible, but about whether string theorists consider space-time as somehow quantized (or discrete), or rather as a continuous manifold, or are both options possible? In other words, can strings move continuously through space, or are there a discrete set of locations where strings can be, and does string theory rule out one of the options?  How about the same question in loop quantum gravity (LQG)? Should I think of the spin networks in LQG as describing a discrete space-time?  Thanks for your insight, or any references you may be able to provide! What can I do to increase battery life on my Android device? What can I do to get better battery life on my Droid? Battery life seems awful. Less than 15 hours or so on normal usage. As a grad student, I just find it tremendously frustrating when emails are ignored by faculty (both at my institution and at other places). Is this acceptable? I'd be content with a simple response with one line along the lines of "I have read this email and am busy right now, will respond in X days when I can write a more detailed email." I understand that, as a first year student in my field, I'm not really in a position to request anything of anyone, but it just seems like common decency.  Instead, I never hear back, as if my email has been jettisoned off into oblivion. Why is '.' a hard link in Unix? Do Stack Overflow and other Stack Exchange sites have an app I can use? I like using Stack Overflow (or any other Stack Exchange sites) and was wondering if there was an app I could install on my phone or other device that would allow me to use the site on-the-go or straight from my desktop.  Some systems to consider:   Windows 8 Android iPhone/iOS   What are some apps that I could install to my computer or phone to enhance my Stack Exchange experience? How does update work with programs installed from .deb file I'm having some difficulties exactly understanding how the the whole update thing work in Ubuntu and good practice for installing software.  I understand I have a  /etc/apt/sources.list file where all my repositories are listed, and that these repositories are queried when I use apt-get update - to later be used with e.g. apt-get upgrade.  This makes perfect sense and I recently installed spotify by adding deb http://repository.spotify.com stable non-free to this "sources" list.    But then I got confused...  When I went to download Google Chrome I merely had to download and grab a .deb file, and Chrome installed with no problem... but I don't see any new entry in /etc/apt/sources.list...  So how does apt-get update know where to query concerning Chrome updates?  Has it somehow been added to one of the already listed repositories in the sources file?  I would like all my installed software to be encompassed by the update function. How do I split a string by a multi-character delimiter in C#? Is Ubuntu compatible with my hardware? I am a bit financially strapped and received a Gateway GT5056 tower. The tower has an AMD dual core 64-bit processor in it. Will Ubuntu 12.04 run on this machine? I will not have any other application other than LibreOffice installed. How would you represent "religion" in an icon, neutrally? Uniform continuity of $\sin(x\sin x )$ for all $x\in (0,\infty)$ Convergence of a sequence implies convergence of the norm of the sequence If $\langle X_n \rangle$ is a sequence in $\mathbb R^n$ then $\lim\limits_{n\to \infty}X_n=A$. Show that $\lim\limits_{n\to \infty} \| X_n \| = \| A \|$ .   My thought process, $\| X_i \|= (\sum_{i=1}^n x_i^2)^{(1/2)}$ therefore be the multiplicative property of limits $x_i^2 = a_i^2$. Therefore the limit of norm of the components is equivalent to the limit of the corresponding limit of each component of the sequence. When there is less than 5% battery left on a mac, the battery indicator goes red and system performance significantly drops - presumably in an attempt to make that remaining 5% last a little longer.   Is there a way to manually trigger this, so that the system performance is low (and battery life longer), even when there is plentiful battery?   This would theoretically be a way of extending the number of hours on a battery beyond the rated amount. Enable 'on the fly' CRS transformation in QGIS 3? I was peacefully playing GTA Online (yeah, was killing someone coming out of ls customs) then a hacker came and killed me using explosive ammos, I called him a hacker and he teleported to me and gave me 790k. I know that people get banned for receiving this kind of money, what should I do to avoid the ban? I have installed VirtualBox OSE on Ubuntu 11.04 and Windows XP pro as the virtual machine. Now I want to have a shared folder which can be accessed on both, my host Ubuntu machine, and my WinXP guest virtual machine.  How can I do that? Flames with no gravity? I was watching  today, and noticed this: in some moment the space station changed orbit and the people inside experienced zero-gravity. At that moment, a candlestick passed floating in the air, with the candles burning ().   But in our environment the flames go upward because the hot air is less dense, and that effect should disappear when no gravity is present, am I right? How would a candle flame look then? How to run Ubuntu without GUI in Virtual Box? What software is used to generate the reputation graphs on Stack Exchange? I'm particularly interested in the zooming functionality which is done very well. Were these graphs generated using off the shelf software or were they coded from scratch? I have a chain object. And i have a curve it follows. I got it to work for following curve, but chain object is not circles but both parts are more like stretched circles (ovals). Object i made with 2 toruses one rotated 90 degrees and then joined them together. I tried single torus too. But same issue. on a curve it just looks stretched oval. What can be the issue?   Thanks