Buying my first off-camera light. Flash or always on-light?
What should I consider when choosing continuous lighting vs. strobes for studio photography?
I have created two files:  sample.txt and sample.txt  (the second file contains some hidden characters, e.g. a space). How can I remove the latest modified file? I'm using Linux. chpasswd apply changes in the chroot directory Using $g = \frac{Gm}{r^2}$, the force on a point mass located at 1 AU from the Sun ($m = 2 \cdot 10^{30} \text{ kg}$) is about ~0.006 N/kg.  Does that mean that, e.g., a 70 kg person is ~42g lighter during the day, and ~42g heavier at night? That seems like it could make a big difference for things like measuring gold bars or other weight-sensitive items. (Gold arbitrage: buy your gold during the day and sell it during the night! Risk-free profit!)  This makes me suspect that I'm overlooking something obvious, because a ~0.05% weight difference seems like something everyone would have noticed long ago. So what am I missing?    Edit: A few answers below indicate that there shouldn't be any weight difference, because the Earth orbits the Sun in free-fall. But if that's the reason, does that mean that a 1:1 tidally-locked Earth-Sun system wouldn't experience differential gravity from the Sun on opposite sides? That doesn't seem right. How to name an item using /give command in MCPE? Global auth is dead! Long live universal login How to stop fluid inflow? I have fluid simulation with an inflow object. I want the inflow to go for 2 seconds, then have the inflow stop (so no more fluid is added) but keep the simulation going  (so the existing fluid sloshes around).  However, I do not see any way to set start and ending values on my inflow object.  How do I stop inflow at a certain frame/time in my simulation? In the movie Iron Man 2, Tony Stark figured out how to synthesize Vibranium. Why didn't he use it to make a new Iron Man armor? block certain dangerous commands? How do I remove/delete a folder that is not empty? I am getting an 'access is denied' error when I attempt to delete a folder that is not empty. I used the following command in my attempt: os.remove("/folder_name").   What is the most effective way of removing/deleting a folder/directory that is not empty? What is the shape of a black hole? I was thinking; what shape does a black hole have?. By 'Shape', I mean its form (e.g, circle , cylinder, sphere, torus, etc..).  We usually think of black holes as if they're plugholes (e.g, a flat circular object), but what if they're spherical? A spherical black hole would make much more sense. I would imagine than a black hole shaped like a basketball would be capable of pulling more mass towards it than a flat one, as it has a higher surface-to-volume ratio to do so.  Edit I know that it's probably a sphere, but when you think about it, a cylinder could also be a potential shape. I don't like having the middle mouse button paste, because I often end up with uncompilable code in Eclipse. How can I turn this off (in all programs)? I'm running Fedora. While studying rotational mechanics, I came across a section where it mentioned that angular momentum may not necessarily be parallel to angular velocity. My thoughts were as follows:  Angular momentum ($L$) has the relation $L=I\omega$ where $\omega$ is angular velocity and $I$ is the moment of inertia, so following this relation, it seems they should be in the same direction. Why are they not? work done is zero if displacement of point of application of force is zero but why can't we assume forces on COM and its displacement What would be an English equivalent for the Mexican Spanish word tocayo? I know that I can make certain blocks only placeable on a specified block, but what is the command to give an item that can only BREAK certain blocks? Linear Combination of Random Normal Variables In order to prove that the linear combination of two independent normal distributions(say Z=X+Y) is normal, i am using their MGFs to show that the linear combination also has a similar mgf. This works okay when Z = X+Y. But when Z=X-Y, i run into trouble :  E[$e^{tZ}$] = E[$e^{t(X-Y)}$] = E[$e^{tX}$]E[$e^{-tY}$]  Now i cannot put this as $M_{x}$(t) * $M_{y}$(t) because of the negative sign. I was surprised to find that standalone package can not compile a document with an equation:  \documentclass{standalone} \begin{document} \begin{equation} % not working! F(V, T) = E(V) + D(T) \end{equation} \end{document}   Is there an option or some workaround that allows this? The current error is something like:   ! Missing $ inserted.   in line 4. (The idea of course is that the including (main) document can just \input the standalone without knowing if is going to be an equation or something else) I already derived a QM expectation value for ordinary momentum which is: $$ \langle p \rangle=  \int\limits_{-\infty}^{\infty} \overline{\Psi}  \left(- i\hbar\frac{d}{dx}\right) \Psi \, d x $$ And I can read clearly that operator for momentum equals $\widehat{p}=- i\hbar\frac{d}{dx}$. Is there an easy way to derive an expectation value for $\langle p^2 \rangle$ and its QM operator $\widehat{p^2}$? How to find correctly the .bib file? I have a .bib document called References.bib saved in the following directory: C:\Users\dvale\Documents\3_References\References.bib  This file contains this entry: @Article{Ballot2014,   author    = {Ballot, Andreas},   title     = {Diversity of cyanobacteria and cyanotoxins in {Hartbeespoort Dam, South Africa}},   journal   = {Marine and Freshwater Research},   year      = {2014},   volume    = {65},   number    = {2},   pages     = {175--189},   issn      = {1323-1650},   doi       = {10.1071/mf13153}, }  I created a document and cited this reference, however the citation is not appearing, apparently because the .bib file was not found. I'm using biber as bibliographic tool (if is important this information). \documentclass[12pt,a4paper]{article} \usepackage{biblatex} \addbibresource[location=remote]{C:/Users/dvale/Documentos/3_References/References.bib} \begin{document} Example \cite{Ballot2014} \printbibliography \end{document}  When I compile the bibliography (F8 in TeXstudio) the following error appears ERROR - Cannot find 'C:/Users/dvale/Documentos/3_References/References.bib'!  EDIT 1: I use JabRef to create my .bib files with UTF-8 encoding The .blg file has the following information in the notepad [0] Config.pm:312&gt; INFO - This is Biber 2.15 (beta) [0] Config.pm:315&gt; INFO - Logfile is 'MWE.blg' [105] biber-MSWIN64:330&gt; INFO - ===  [127] Biber.pm:415&gt; INFO - Reading 'MWE.bcf' [234] Biber.pm:952&gt; INFO - Found 1 citekeys in bib section 0 [251] Biber.pm:4334&gt; INFO - Processing section 0 [267] Biber.pm:4523&gt; INFO - Looking for bibtex format file 'C:/Users/dvale/Documentos/3_References/References.bib' for section 0 [502] Utils.pm:411&gt; ERROR - Cannot find 'C:/Users/dvale/Documentos/3_References/References.bib'! [502] Biber.pm:132&gt; INFO - ERRORS: 1 Normalising Constant for exponentiated function What would the normalising  constant be of the following, or atleast an approximation? I would like to avoid sampling.  $$f(\theta)=\exp(-k_1e^{-k_2\theta^2}-\theta^2)\qquad\theta\in(-\infty,\infty), \quad k_1,k_2&gt;0$$  In the event that its not possible, what would be a valid polynomial lower bound on $\log(f(\theta))$, that would take into account $k_1$  For anyone, who is interested, I end up with this expresssion because I place a Gaussian prior over (a squared exponential) kernel parameters, and trying to use variational bayes (hence, a lower bound).