The disparity between screen sizes is the result of a battle for viewers that has been waged between the big screen of cinema and the small screen of television. Many wonder why the TV was designed as a square since most movies are rectangular in shape.

It didn't used to be that way. When televisions began to spread in 1950s, the square image area of the small screen was proportional to what you'd find in your local cinema as well. So, don't bother trying to hunt down that elusive widescreen edition of Citizen Kane -- movies of that vintage just weren't as rectangular. Their then-standard size determined the aspect ratio used in the manufacturing of televisions. [emphasis mine]