I am a degree student and .. A loner. During my free time, I usually try to observe my surrounding more, you know... :\ Here's the experiment I did (I saved it in my note app, copied it directly from there): A certain window has a point of view (not referring to the meaning where point of view means opinion) Just perform these steps: 1. Place your index finger on the window, PERPENDICULAR to the window surface. 2. Then position your head just behind your finger which is perpendicular to the window. 3. Now watch from that view (exactly from the straight view of your index finger) 4. Note (or remember) the place to which your Index finger points to. 5. Repeat the above 4 steps by placing your index finger on different points on the same window. I would appreciate anyone's explanation based on my (or if you performed this then yours) explanation. Thank you.