by 
The red line on this world map looks all curvy, but in reality is a perfectly straight line. Remember, the earth is spherical, so any straight line drawn on the surface of the earth will appear curved in a flat projection of a map, if the line is long enough. This is why satellite paths when mapped over the earth’s surface appear like sine waves. The reverse is also true: any straight line on a flat map is actually a curved path.
This particular red line is special, because it represents the longest straight-line sea journey anybody can take without hitting land.
Source / Image Courtesy
