What exactly IS voltage and its difference to other measurements of electricity? I apologize if this is a stupid question, but I cannot find any answers online, so I feel I must ask here.  I do not quite understand exactly what voltage is. I see on batteries, "X Volts", but I do not quite know what that means. I looked online and read sources on volts, amperes, and watts, and it has only confused me more. What exactly is voltage? If it isn't a measure of the electric current, then why is it used on batteries as a measure of their electric power? Why aren't amperes used?
What exactly is voltage? Bit of a strange question, but what is it? My physics teacher said it was kind of like a "push" that pushes electrons around the circuit. Can I have a more complex explanation? Any help is much appreciated.
I have an intuitive scenario. Consider we have a spaceship just below the event horizon of a BH, which is merging with another black hole.  Finally, the singularities merge and we have a single black hole again.  But, in the transient stage, it is unclear to me if a timelike world-line would exist to leave the system.  I suspect, the metric is probably far too complex for an analytical solution, but in the worst case, it could be maybe solved numerically.  As far I know, black hole merges are examined mainly in an inspiral scenario. I suspect, maybe the escape is possible only if they have a hyperbolic-like orbit (i.e. there is no inspiral, but they simply collide).  Is it possible? I want to save a backup of my data on a remote server, but never want the backup server to see the data unencrypted. Editing a single file and backing up should not result in everything being encrypted and sent again. The remote server should preferably not even know the directory structure (and especially not the directory names).  Is there such a solution? Why is Cat5/Cat5e Ethernet cable rated 100MHz? As the questions says, is there any specific reason why Ethernet cable is rated 100MHz?  For a 100Mbps Ethernet the data rate is 100Mbps, and the baud rate is 125Mbaud, because of the specific line coding that it uses. What is the relationship between 125Mbaud rating of data transfer and 100MHz rating of cable?  Thank you. Using Gnome 3.18. I share files between other family members, but the default umask on my distro (archlinux) is 0022. So every file/directory created is not writable for our common group.  I tried to put umask 0002 in /etc/profile but the gnome session is still using 0022. It's working for a login bash shell, though.  I also tried to add this line in /etc/pam.d/system-auth:  session   required  pam_umask.so umask=0002  It has the same effect as the one in /etc/profile. I tried  If I change the umask manually in a gnome-terminal shell, then I launch an application from it, say gedit, then the files created by it have the wanted permissions. If I launch gedit from the gnome menus, it doesn't. So my matter is really to set the umask for the gnome session, and I can't find where to do it.  EDIT (to answer Gilles' comment): I'm using gdm 3.18 as the DM. I also tried to add the pam_umask line into /etc/pam.d/gdm-launch-environment. All other gdm-* files contains includes of session from the system-auth file, so they should not need more. It doesn't change anything.  /etc/login.defs contains UMASK 077 but also USERGROUPS_ENAB yes which should set the umask to either 0077 or 0007 for users whose primary group is the username.  The only file that contains 022 for umask in /etc is /etc/profile but that was my first try.  As for /etc/Xsession.d, I don't have this directory. Besides, as wayland is now the default display server, I'm not sure the umask should be set as part of X initialisation, even if I'm still using it myself. What does if __name__ == "__main__": do? Is there any SCP program available for Ubuntu that does not require SFTP on a remote host? I need a program that can manage files on a remote device running Linux using SCP. The remote device runs OpenWrt. On Windows there is a perfect one WinSCP. it is weird that there is no native program that can be used. The program should be able to:  list files copy and move files to/from the device and within the device. delete files on the device view and edit files change file permissions  I have found only one alternative, except using CLI and installing WinSCP with wine. It is Midnight Commander with fish. It works really poor. The problems are:  It mixes up ~ on a remote device and on the computer. It can't edit files. I can open and edit, but they are saved to a wrong place.  There is a lot of other annoying problems that makes it almost unusable. I gave up using mc and now I am using pure shell on the remote device. Please do not tell me that Nautilus, etc support these features. They don't!!! Linux native file managers require SFTP that is not available on the remote device. Maybe it is possible to get nautilus use SCP, but I did not find a way of doing it without changing sources. THIS IS NOT A DUPLICATE !!! I have a specific requirement that is not covered in the duplicate question. If it is not possible on Ubuntu, then this could be an answer. This question is in the spirit of , an example of an apparently non-deterministic system in Newtonian mechanics. Under certain restrictions, the  guarantees the existence and uniqueness of solutions to differential equations with initial conditions. However, Norton's dome does not satisfy these restrictions. The ball may sit on top of the dome for an arbitrary period of time before sliding down in a particular trajectory, without violating Newton's laws of motion.    Is there a plausible example of a system of interacting point-particles such that the equations of a point-particle are continuous but not , and therefore fail to have a unique solution? How do I enable or disable Apport? The system crash dialog is annoying me, how can I turn it off? I'd also like to know how to turn it back on just in case I need it to report a problem. Equation left margin Enable HTML5 tags on Eclipse I really love Eclipse (PDT)... But i'm developing sites using HTML5 and CSS3 and it mark the HTML5 tags like &lt;nav&gt;, &lt;section&gt; and &lt;article&gt;  as invalid tags (inexistent).  How can I add those new tags to it?  And what about CSS3 rules?  I read something about remove the "invalid tag" check... and that's not what I want. :( Can we exempt downvoted accepted answers from getting the top spot? Decision boundaries and Gaussian density functions What is the difference between HTML tags  and ? I would like to ask for some simple examples showing the uses of &lt;div&gt; and &lt;span&gt;.   I've seen them both used to mark a section of a page with an id or class, but I'm interested in knowing if there are times when one is preferred over the other. Why am I forced to use the newest chat interface? When logging into chat-stackexange I am presented with this message:  The new mobile version of chat is now the default mobile version on devices that support it. Unlike the classic (okay, ancient) version, it allows you to perform actions like editing, starring, and direct replies to particular messages. The classic version is still available and will be used in browsers that lack support for some necessary features of the new version. Logged in users can also choose to continue using the old version on the preferences page of their user profile. Please report bugs and other issues on Meta Stack Exchange. Thank you!  I choose to continue using the old version but cannot find the option to do so on my chat user profile page? Fastest converging method for calculating e How to split algorithm2e over two pages Downloading multiple files with youtube-dl I use youtube-dl to download files from YouTube. I have tried downloading multiple files, but it is not working out for me. I have to open multiple terminals and start afresh every time I want to download a video.   Can you help me to download multiple files with a single terminal window by just mentioning all the URLs at once? I use Ubuntu 12.04 64-bit. When using data.stackexchange.com I fail to remember if as [post link] is the correct alias to get the url for the post. Luckily the site has an  link. Unfortunately it is now broken. Can this be fixed? I suggest that when a post is migrated from one site to another, that the question vote score get reset to zero (or perhaps only a negative vote score is reset to zero). Often people will downvote a question when the only thing that's "wrong" with it is that it's posted on the incorrect site. After migration, those downvotes hang around as a negative score and may unfairly bias the treatment of the question. What do I say to make a new line when using voice recognition? I've found I can make punctuation happen by saying "comma", or "period", but I can't find the word for new line.  I tried "paragraph", and "line break", but it just prints those words.