Can the laws of gravitation be extended to two energies? Is there a a force of attraction similar to gravity among two energies? (Excluding things like magnetic or electric attraction).
As small as it may be, does every 'thing' have a gravitational pull?  That is, something with mass or energy. No matter how obsolete or negligible it may be, is it there? If so, how is it calculated? What does 'it' affect?
Is there a way to spellcheck the word under the cursor with a keyboard shortcut? I have B1/B2 Visa. Can I travel for Business trip to US with this Visa? I have been given B1/B2 Visa, but first time when I had applied, it  was for vacation &amp; holiday. Now I need to go to US for business meetings. Is this Visa good enough or do I have to apply for a B1 Visa again?  Note: I originally applied for vacation purposes, but in my visa it is stamped "R b1/b2" Across the Stack Exchange network you may leave comments on a question or answer.  How do comments work? What are comments for, and when shouldn't I comment? Who can post comments? Who can edit comments? How can I format and link in comments? My comment doesn't contain some of the text I typed in it; why? My comment appears to be long enough, but I can't post it because it's too short; why? Who can delete comments? When should comments be deleted? Why can't I comment on specific posts even if I have enough reputation to comment? When can comments be undeleted? What are automatic comments? How can I link to comments? Anything else I should know about comments?  Also see the FAQ articles on  and . Flex-box: Align last row to grid Trying to find some simple SQL Server PIVOT examples.  Most of the examples that I have found involve counting or summing up numbers.  I just want to pivot some string data.  For example, I have a query returning the following.  Action1 VIEW   Action1 EDIT   Action2 VIEW   Action3 VIEW   Action3 EDIT     I would like to use PIVOT (if even possible) to make the results like so:  Action1 VIEW EDIT   Action2 VIEW NULL   Action3 VIEW EDIT     Is this even possible with the PIVOT functionality? How to copy the complete folder structure one location to another location include all files and sub folders I have folder structure like in Shared documents/East using CSOM and C# Main Folder   Folder1   Folder2      File1      File2  I have to copy all folders with files to Shared documents/West .... I need to include a couple of Python code listings, where the indentation of the lines (using some number of spaces) is significant. I would like for the code listings to be copyable, so the spaces at the beginning of the line need to be be copied along with the text.  This question has been asked in various ways before (e.g. , or ). Those questions focus on making line numbers uncopyable, though.  Making the spaces at the beginning of a line copyable seems to be harder: "I am not sure it is possible to specify in the PDF (at least in a viewer-independent way) that the indentation should be copied too" (). At , Philippe Goutet suggests a solution (turning the spaces into visible spaces, and coloring them in the background color so that they appear invisible) that works using Acrobat Reader, but not all readers. He says "It works under Acrobat Reader and it's extremely pleasant to be able to quickly copy/paste code without problem (perhaps the problem can be circumvented by writing direct PDF code to tell that it's a space, I've never had the time to try)".  Is it possible to produce a PDF with a code listing with copyable real spaces at the beginning of a line?  Minimal example: The line return x should start with four spaces.  \documentclass{article}  \begin{document} \begin{verbatim} def myfunction(x):     return x \end{verbatim} \end{document}   I know that I could attach the code to the PDF as a file, but that's not what I want. Can't convert string into float/double Proving that the difference of the terms of a sequence, multiplied by $n$ converge Proof by induction of summation inequality: $1+\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+\dots+\frac1{2^n}\ge 1+\frac{n}2$ Prove by induction the summation of $\frac1{2^n}$ is greater than or equal to $1+\frac{n}2$.  We start with $$1+\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+\dots+\frac1{2^n}\ge 1+\frac{n}2$$ for all positive integers.   I have resolved that the following attempt to prove this inequality is false, but I will leave it here to show you my progress. In my proof, I need to define P(n), work out the base case for n=1, and then follow through with the induction step. Strong mathematical induction may be used.  This is equivalent to $$\sum_{k=0}^n\frac1{2^k}\ge 1+\frac{n}2\;.$$  Let $P(n)$ be summation shown above.   Base case for $n=1$, the first positive integer,   $$\sum_{k=0}^1\frac1{2^k}=\frac1{2^0}+\frac1{2^1}=1+\frac12=\frac32\ge 1+\frac12=\frac32\;,$$  so base case is true.  Induction step: Assume $P(n)$ is true and implies $P(n+1)$. Thus   $$\sum_{k=0}^{n+1}\frac1{2^k}\ge\frac1{2^{n+1}}+\sum_{k=0}^n\frac1{2^k}\ge 1+\frac{n+1}2\;.$$  This can be written as   $$\sum_{k=0}^{n+1}\frac1{2^k}\ge \frac1{2^{n+1}}+1+\frac{n}2\ge 1+\frac{n+1}2\;.$$  I work the math out but I get stuck contradicting my statement. Please show your steps hereafter so I can correct my mistakes. Does excessive markup affect SEO? How can I find the source of a mysterious bad smell? We have recently moved home, and all is fine appart from a mystery smell which I'm unable to track down. It's driving me crazy (actually, my wife thinks I am crazy as she can't smell it).  I'm hoping someone on here could offer some tips on how to track it down, or what it might be.  Here's some info:  Background: The house is a two floor (plus basement) block/concrete construction.  There is a wide hallway on the groundfloor connecting the rooms (including kitchen, toilet/shower room, stairwell).  The stairs are wood-board on concrete.  The floor in the hall and kitchen  is tiles over concrete, the rest woodblock/parquet over concrete.  Location of the smell: I usually smell it when coming down the stairs, seems to be strongest about half way down.  However sometimes it doesn't smell on the stairs at all, but rather in the ground floor hallway.  Seems to move around quite a lot. Occasionally I have felt it upstairs, but assume this is it drifting. The basement smells fine.  The Smell: The best description of the smell I can give is something like old rubbish.  What I've investigated so far:  1) Something died somewhere?  This was my initial thought, and since I usually notice the smell on the stairs I thought I'd try there first.  I've taken up some of the wood on the stairs (not all yet) but not looking promising, as there really isn't much space between the wood boards and the concrete.  Not really sure where else something could have gotten, as everything seems to be tight against the concrete.  2) Smell from kitchen moving into rest of house? I never really detected a bad smell in the kitchen, but thought I'd rule it out anyway. I thought maybe it was the bin under the kitchen sink that might be causing it.  So I moved the bin to a small storage room at the back of the kitchen (and kept the door closed) and thoroughly cleaned inside the cupboard under the sink. No change.  I also looked behind all of the cabinets for a problem, but could not see anything.  3) Gas from drains? The sink doesn't smell in the kitchen, and it's got a P-bend trap on the pipe - so I can't see a problem there.  Cant detect a smell from the plugholes in the bathroom either.  The bathroom sink waste pipe has a bottle-trap on it.   Don't know if there is a trap on the shower as it's a sealed unit, but I'm guessing yes (and can't smell anything).  Can any one think of something I might have missed, or give any advice? I have three partitions on my drive, arranged something like the following:   ___________ | 1 |  2 | 3| -------------   I wish to merge partitions 1 and 3.  Is there a way to do this, or do I have to manually "slide" partition 2 over to partition 3, and then merge the newly open space where partition 2 used to be?  Note: I do not have the space to copy partition 2 to partition 3 (2 is 200GB and 3 is 65GB). How to create immutable objects in Java? Is there a statement whose undecidability is undecidable? We know there are statements that are undecidable/independent of ZFC. Can there be a statement S, such that (ZFC $\not\vdash$ S and ZFC $\not\vdash$ ~S) is undecidable? How can I re-enable backspace navigation in Chrome? Is there any scientific experiment that can lead us to conclude we live in 3 spatial dimensions without the premise of the conception of limited dimensions?  Thank you all who helped in the improvement of this question (which was not clear at first).   EDIT:  I know that this can be a little philosophical, but it is also a scientific question.  Let's consider the scenario where the mankind was not ever able to see.  Let's also consider that this limitation could be surpassed thus not limiting us to reach a scientific and technological knowledge "similar" to what we have today.  Would this civilization of blind people reach the conclusion that they are living in a 3D spatial world?  Is the sense of touch enough to reach that conclusion? Is there any scientific experiment that can lead us to that conclusion without the premise of the conception of limited dimensions?  Would it be easier, harder, or just different to reach a conclusion predicted by the M-Theory? (please do not focus only on this last question) Is there such a thing as a European SIM card? This summer I will go on a road trip from West to East Europe and back. Being able to call and especially access the internet is useful on the road, so it made me wonder whether I could buy a European SIM card or something that would let me access the web or make calls regardless of the country I was in.  I know of the provider Mobile Vikings that offers a . Are there any other alternatives? Data is the main priority because calling or texting within Europe isn't that expensive to begin with, with recent regulations. Also I could use the data to call using VOIP anyway, which is even cheaper. Find $ \lim\limits_{ x\to 100 } \dfrac { 10-\sqrt { x } }{ x-100 }$  (without using a calculator and other machines...?) glob() - sort array of files by last modified datetime stamp