In special relativity it is said that " Time and space cannot be defined separately from one another. Rather space and time are interwoven into a single continuum known as spacetime. " What is the exact meaning of this statement ? In SR, even though time is relative too but still in classical physics, we still needed time to define an event and what is the meaning of the term continuum ?
I'm having a hard time understanding how changing space means changing time. In books I've read people are saying "space and time" or "" but never explain what the difference is between the two concepts or how they are related.  How are the concepts of space, time, and space-time related?
There is no continuous injective function $f:\mathbb{R}^n\longrightarrow\mathbb{R}^m$ Orbiting a specific point - Orbiting Camera How would I create a camera that with the mouse, it allows you to orbit around a specifc position, with the camera always facing that point? I would also like it to be able to always be at a constant distance from the point, and be able to orbit around it in every direction.   Any ideas? Getting Started With Java EE I am about to start a web project and have been working almost exclusively with a LAMP stack for the past 5 years.  I would like to build something larger and more scalable and hence have been looking into Java EE.  The division of logic between JSP and EJB seems ideal for what I want to do.  Can anyone recommend resources for getting familiar with Java EE?  And perhaps if anyone knows of technologies that are more scalable than PHP that I should consider as well, I'm all ears.  Thanks a lot! Grass tools not working in QGIS 2.14.3-ESSEN, OSGEO4W Is short-circuiting logical operators mandated? And evaluation order? Isometry from Manhattan plane to Euclidean plane? Does there exist an isometry from a Manhattan plane $A$ to a Euclidean plane $B$? I.e. a function $\varphi:A \to B$ that suffices $\|\varphi(a)\|_B = \|a\|_A$ for all $a \in A$, where  $\| \cdot \|_A$ is the Manhattan norm and $\| \cdot \|_B$ the Euclidean norm. Err 80 appears when I turn on my Canon EOS 5D Mark II What is the best choice for .NET inter-process communication? Does this constitute a valid proof that $\frac{x^2}{1+x^4} \leq \frac{1}{2}$? Why getting this error tlmgr Unknown directive? I haven't used tlmgr for a while but when I tried to install any package with it today, It returned following message:     (running on Debian, switching to user mode!) Unknown directive ...containerchecksum c59200574a316416a23695c258edf3a32531fbda43ccdc09360ee105c3f07f9fb77df17c4ba4c2ea4f3a5ea6667e064b51e3d8c2fe6c984ba3e71b4e32716955... , please fix it! at /usr/share/texlive/tlpkg/TeXLive/TLPOBJ.pm line 210,  line 5579.   I've tried to use fix specified on :     You have to download update-tlmgr-latest.sh from the tlpretest repository   and run it. Afterwards you will be able to work with tlmgr as usual   (announced by Norbert a few hours ago).   I've downloaded it from , but it returned another error:  Verifying archive integrity... All good. Uncompressing TeX Live Manager Updater............................................................................................................................................................................ ./runme.sh: Cannot find TeX Live root using kpsewhich --var-value=SELFAUTOPARENT. ./runme.sh: Please set your PATH as needed, otherwise it's hopeless.   Minimum example  Install cleanly vanilla TeXLive 2016 with tmlgr after having old TeXLive in the system successfully: there is no errors/warnings in /usr/local/texlive/2016/*.log, complete log example . Run the following but you get the same output as above when trying to update the system  root@masi:/home/masi/Downloads/t/install-tl-20161019# tlmgr update --self (running on Debian, switching to user mode!) Unknown directive ...containerchecksum c59200574a316416a23695c258edf3a32531fbda43ccdc09360ee105c3f07f9fb77df17c4ba4c2ea4f3a5ea6667e064b51e3d8c2fe6c984ba3e71b4e32716955... , please fix it! at /usr/share/texlive/tlpkg/TeXLive/TLPOBJ.pm line 210, &lt;$retfh&gt; line 5579. What is a command to compile and run C++ programs? I am  new to Linux. I am using Ubuntu 11.04 and do not know how to compile and execute C++ program in it. I need to know the commands to Compile and Execute a C++ program in Linux. How do you improve Drupal performance? Drupal is fast at develop, but the performance is so poor.  It is hard to reach 50 request per second.  And there are so many SQL queries in a simple web page.  If you test the request time of a form submit in Drupal.org it will always take seconds to finish.  How do you improve the speed of your web site? Can you find all classes in a package using reflection? Multiple domains for different products? I have a website with software applications. Is it good for SEO to choose one keyword rich domain name for each of our software products or should we stick to a single domain?  From a user's perspective I think it would be easier to remember a domain that is keyword rich as the user will instantly know what this product is for.  But I have read articles that the latest trend in SEO is to stick to one domain for all of your products and invest on this single domain website.  Is that true? What do you advise? Should I register a separate domain for each of our products or should I use only one single domain?  Should I do a 301 redirect with a .htaccess to a single domain? And what about the sitemaps? Should I register all sites in Google Webmaster Tools and post a separate sitemap for each one of them? should my main site sitemap include all pages or should separate domains have their own sitemaps? Which is the simplest way to update a Label from another Thread?   I have a Form running on thread1, and from that I'm starting another thread (thread2).  While thread2 is processing some files I would like to update a Label on the Form with the current status of thread2's work.   How could I do that? So, I'm working on a control station that has buttons. It is a one-mesh creation, that means, I don't want to create buttons and things like that separated from the main mesh, but as you can see, I have problems. I would like to make the highlighted parts to be one with the main part around them. I've tried everything, and I have this problem on multiple creations. Any idea?  Update: I've added another example of the problem. I want them to be one face, instead of two. (2nd picture) Find a non-negative function on [0,1] such that $t\cdot m(\{x:f(x) \geq t\}) \to 0$ that is not Lebesgue Integrable Laptop (Asus x555u) screen turns off as soon as you remove the power cord Unable to catch JsonMappingException Why is unity feedback used? Why is the unity feedback system used? This block diagram is for a 2 DOF ball balancing using a PID controller.