Some stupid meme my sister showed me went along the lines of &quot;will my laptop get heavier if I put more files in it?&quot;, but it was sufficient to get me thinking--is there an energy change &amp; associated mass change when a file is written to a solid state drive? I don't know enough about how a solid state drive works to know for sure... but my intuition says that for highly compressed files, the informational entropy is probably the same as an unwritten (sector? Again, I don't know that much about SSDs). However, I wonder if highly organized/low entropy files, such as uncompressed text files or bitmaps, would affect a change in the mass of the drive, one way or another.
Browsing Quora, I saw the following  with contradicting answers.  For the :     The bits are represented by certain orientations of magnetic fields   which shouldn't have any effect on gravitational mass.   But,  contradicts that one:     Most importantly, higher information content correlates with a more   energetic configuration and this is true regardless of the particular   type of storage... Now, as per Einstein's most famous formula, energy   is equivalent to mass.   Which answer is correct?
DNS Resolution for example.com - Can you explain? It appears that in PHP objects are passed by reference. Even assignment operators do not appear to be creating a copy of the Object.  Here's a simple, contrived proof:  &lt;?php  class A {     public $b; }   function set_b($obj) { $obj-&gt;b = "after"; }  $a = new A(); $a-&gt;b = "before"; $c = $a; //i would especially expect this to create a copy.  set_b($a);  print $a-&gt;b; //i would expect this to show 'before' print $c-&gt;b; //i would ESPECIALLY expect this to show 'before'  ?&gt;   In both print cases I am getting 'after'  So, how do I pass $a to set_b() by value, not by reference? Intuitive explanation of unit root How would you explain intuitively what is a unit root, in the context of the unit root test?   I'm thinking in ways of explaining much like I've founded in .  The case with unit root is that I know (little, by the way) that the unit root test is used to test for stationarity in a time series, but it's just it.   How would you go to explain it to the layperson, or to a person who has studied a very basic probability and statistics course?  UPDATE  I accepted whuber's answer as it is what most reflect what I asked here. But I urge everybody that came here to read Patrick's and Michael's answers also, as they are the natural "next step" in understanding the Unit Root. They use mathematics, but in a very intuitive way. Selecting the Real Analysis Textbooks I am a sophomore in US with double majors in mathematics and microbiology. I am interested in self-studying the real analysis starting now since it will help me on my current research on computational microbiology, prepare for upcoming math research (starting on this Fall) on the analytic number theory, and prepare for the real analysis course I will take on Fall and Putnam competition. I just finished "Calculus with Analytic Geometry" by G. Simmons, "How to Prove It" by Daniel Velleman, and "How to Solve It" by G. Polya. I also read some portions of Apostol's Calculu Vol.I to get a deeper view on the calculus theories. I was originally planned to read Apostol's Calculus Vol.I and Spivak's Calculus first, but I think it would be a better idea to start with real analysis since it covers all ideas in those "advanced calculus" textbooks and much more. My current plan is to start with one "dumbed-down" real analysis textbook and one "comprehensive, detailed, and intermediate" textbook, and advance into Rudin's PMA (required textbook for my real analysis course) starting on Summer and use it in accordance with other real analysis textbooks. Could you help me on selecting one book from each category?   Elementary Real Analysis textbooks:  **Elementary Analysis: The Theory of Calculus (Kenneth Ross)  **Understanding Analysis (Steven Abbott)  **The Way of Analysis (Robert Strichartz)  **Real Mathematical Analysis (Charles Pugh)   Intermediate, detailed Real Analysis textbooks:  **Mathematical Analysis (Tom Apostol)  **Undergraduate Analysis (Serge Lang)  **Introduction to Real Analysis (Bartle, Sherbert) **Elements of Real Analysis (Bartle, Sherbert)  **Mathematical Analysis I (Vladimir Zorich)   Thank you very much for your time, and I look forward to your advice!   Sincerely, PK Cleaning ‘staining’ off bottom of MacBook screen A couple months ago, I started to see some very small stain spots on the bottom of my MacBook Pro early 2015 screen. It's very annoying to see while I'm using it. When the screen is turned off, I see it as in the picture below. But when it's turned on, I see it as very small water-ish drops. I tried to clean it using water, screen cleaner, and even alcohol, but it didn't go away.  Also that area doesn't feel as smooth as the unaffected area. So, I think it's on the outside of my screen not inside.  Have you ever seen this before? Any suggestions on how to remove it without the need of replacing the whole screen? How to do relative imports in Python? Fetching all (javascript) global variables in a page Before I met her I had a poor opinion of her.   As person had a poor opinion before a particular time in past (before He met her) so I think there should be had had.   There are some more example like this:   Before I went to the university, I worked/had worked as a carpenter for 5 years. Before I opened the door, I put/had put the key in the lock. Before I opened the door, I looked/had looked carefully into the barn for snipers.   In all these sentence, for me, it should be perfect tense.  I asked that question on another platform where I was told that if sequence of past event is obvious and sentences uses "before"and "after", we often use past tense. Which means we should use past tense in all these sentences. But I have another sentence "The train had left before I reached the station." If I follow above mentioned rule there should be "left" instead of "had left". But I am damn sure this sentence is correct with "had left".   Am I correct?  Thank you C# - Keyword usage virtual+override vs. new What are differences between declaring a method in a base type "virtual" and then overriding it in a child type using the "override" keyword as opposed to simply using the "new" keyword when declaring the matching method in the child type? I have a PHP script that can encode a PNG image to a Base64 string.  I'd like to do the same thing using JavaScript. I know how to open files, but I'm not sure how to do the encoding. I'm not used to working with binary data. Why are Marketing Cloud timestamps not stored in the same timezone as Sales Cloud? I want to be able to have LinkedList.contains() return true for a custom comparator.  Suppose that I have 1 LinkedList and 2 objects  LinkedList&lt;MyObject&gt; myList = new LinkedList&lt;MyObject&gt;();  MyObject a = new MyObject("HELLO"); MyObject b = new MyObject("HELLO");   Technicaly, both objects are identical in terms of comparison (MyObject implements Comparable)   ( a == b ) == true  however, when I do the following, myList does not return true for myList.contains(b)  myList.add(a) myList.contains(b) // == false   I think its because contains will check object reference and see that a and b are 2 distinct objects. Is there any way I can make it so I don't have to extend LinkedList to compare those objects? Smeared creamy look effect i came across a photo where the gradient looks like it s smeared from cream. It is hard to explained by saying so here is the  Let say i create 2 similar shapes with the gradient pattern then adjust the opacity but the edges will still remain. But in the example the edges are appeared to be soft and hard randomly. Thanks in advance ! "Temporarily unreachable" when using fetch as Googlebot from Webmasters Tools The page I'm trying to fetch is public.  The server logs show no request.  Google reports that any page on my site is "Temporarily unreachable". It won't even fetch the verification file, a static HTML file that was successfully used to verify with the webmaster tool application itself.   My site is running on the .  What is causing this? How do I draw text at an angle using python's PIL? Using Python I want to be able to draw text at different angles using PIL.  For example, imagine you were drawing the number around the face of a clock.  The number 3 would appear as expected whereas 12 would we drawn rotated counter-clockwise 90 degrees.  Therefore, I need to be able to draw many different strings at many different angles. Add high-resolution-graphics and / or .svg-icons I read this at least 20 years ago, and I believe it was originally published in the '60s.   The main character is a human, but somehow "inherits godhood" from an alien, whose species is very long lived. IIRC this is one of the old-style god thingies, i.e. "god of thunder" not "omniscient omnipotent omnipresent transcendent being".  The plot somehow revolved around identifying and fighting some enemy which, I believe, was in turn a member of the alien species who acted as the avatar of the opposite god in the alien pantheon.  The only thing I remember for sure is that the enemy was identified as "green green" or "gringrin" (sadly, I read this in translation so I am not sure what the original meant) Explosive AR(MA) processes are stationary? This doesn't work:  tar xf /tmp/foo.tar.gz foo/bar tar: foo/bar: Not found in archive   It's not obvious to me what would do this beyond extracting it in place and moving the files over. This is a general, community wiki  question to address non-specific "I need a CMS or Wiki that does x, y, and z..." questions.  If your question was closed as a duplicate of this question and you feel that the information provided here does not provide a sufficient answer, please open a discussion on .    I have a list of features that I want for my website's Content Management System (CMS) - where can I find a [free] script that includes all of them?