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Jumping in an elevator? Microsoft.Office.Interop.Excel doesn't work on 64 bit I am attempting to settle a friendly bet.  Would a pendulum swing indefinitely in a hypothetical vacuum (i.e. no air resistance) having a hypothetical frictionless bearing (i.e. no energy lost due to friction) assuming the following   The frictionless vacuum is on Earth (9.8 m/s^2). The pendulum is already in motion and no other external forces other than gravity act on the pendulum. Can you set custom ringtones for contact groups? In iPhone, you can easily change the default ringtone (Settings → Sounds → Ringtone) and set a custom ringtone for individual people (Contacts → [some person] → Edit → Ringtone).   But can you set a custom tone for a group of contacts? (E.g. "family" or "workmates".)  I think that would be handy—and quite basic functionality, so to speak—but I couldn't find a way to do this through the iPhone UI. Is it possible at all (without jailbreaking)? Identifier for win64 configuration in Qmake Is there a "win64" identifier in Qmake project files?  documentation does not mention other than unix / macx / win32.  So far I've tried using:  win32:message("using win32") win64:message("using win64") amd64:message("using amd64")   The result is always "using win32".  Must I use a separate project-file for x32 and x64 projects, so they would compile against correct libraries? Is there any other way to identify between 32-bit and 64-bit environments? Is the double-slit experiment typically carried out in a vacuum? It is my understanding of the double-slit experiment that when a measuring device is activated, to measure which of the two slits a particle is travelling through, this measuring is responsible for a different outcome than when the device is left off. When the device is left off particles leave an interference pattern, suggesting a single particle (or its wave) interferes with itself; when the device is activated no interference pattern is left, and particles are observed to travel through a single slit.  Now, does all this imply that this experiment is typically carried out in a vacuum? If not, how is it that interaction with other particles in the environment of the experiment's set-up are not already influencing the outcome, regardless of whether the measuring device is on or left off?  This question may very well be a very naive one, due to my very limited understanding of particle interaction, vacuums and/or physics in general. If so, I would appreciate a brief, layman's, overview of where my understanding of the different subjects at play here is likely to be lacking. Prove that $(n-1)! \equiv -1 \pmod{n}$ iff $n$ is prime [Wilson's Theorem] How can I show that $(n-1)!\equiv-1 \pmod{n}$ if and only if $n$ is prime? Thanks. Long-distance Mind Trick In the Star Wars universe, could a Jedi Mind Trick be performed over the telephone?   For instance, could Yoda have called up the Imperial embassy on Dagobah and mind tricked whoever answered into getting him in touch with Palpatine? (I know there's no embassy or telephones on Dagobah, but serious question nonetheless.)   To clarify, are long distance mind tricks not only possible but would being in communication with another person, through telecommunication, allow a force user to better perform the action? MySQL ERROR 1045 (28000): Access denied for user 'bill'@'localhost' (using password: YES) A very compact list in Beamer I would like to make a very compact list (e.g., itemize) in Beamer.  has been asked for an article-type document class; the answer uses the enumitem package, known to be .  My question is: How do I make the same compact list in the Beamer document class? As in the above linked question, I would like the list to have   No whitespace before list No whitespace after list No whitespace between lines Less indent before the bullet points How do I stop my rim brakes making a squeaking/squealing sound? I bought a Schwinn Frontier Sport few months ago and started riding happily. After a few weeks my front rim brakes started creaking. It's so annoying in public places. My rear brake doesn't produce any sound but isn't as powerful as the front brake.  The retailer says cleaning would solve the front brake's issues and I got it cleaned, but nothing changed. Is there something I can do something myself to fix this? How did Princess Leia survive this? In the Last Jedi movie, there is a scene where      her spaceship is taken down, Princess Leia is thrown into outer space, and seen floating there, frozen.    However, she manages to survive this, while any ordinary human being couldn't.   How did she manage this? Is this done by using the Force? How do I concatenate const/literal strings in C? When should I begin publishing? Inspired by , say you have a 4x4 two dimensional array, write a function that rotates it 90 degrees. Raymond links to a solution in pseudo code, but I'd like to see some real world stuff.  [1][2][3][4] [5][6][7][8] [9][0][1][2] [3][4][5][6]   Becomes:  [3][9][5][1] [4][0][6][2] [5][1][7][3] [6][2][8][4]   Update: Nick's answer is the most straightforward, but is there a way to do it better than n^2? What if the matrix was 10000x10000? OS volume shows as type 'FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF' Take a screenshot of a webpage with JavaScript? Plot showing discontinuity where it shouldn't How check if a picklist value is available or not for a specified record type ( through SOQL)? Thanks in advance Prove that for all $n&gt;2$ there exists at least one prime $p$ such that $\sqrt{n}&lt;p&lt;n$ using elementary methods.  My try: If not, $\sum_{p&lt;\sqrt{n}} (\lfloor n/p \rfloor-\lfloor \sqrt{n}/p \rfloor) \geq n-\sqrt{n}$  then...?