Tarkovsky developed a theory of cinema that he called "sculpting in time". By this he meant that the unique characteristic of cinema as a medium was to take our experience of time and alter it. Unedited movie footage transcribes time in real time. (The speedy jump-cutting style that is prevalent in music videos and many Hollywood movies today (2007), by contrast, overrides any sense of time by imposing the editor's viewpoint.) By using long takes and few cuts in his films, he aimed to give the viewers a sense of time passing, time lost, and the relationship of one moment in time to another.
I'm not making this up....
I once sat in a restaurant in Los Angeles listening to a guy who looked exactly like Tarkovsky explain to his female companion the theory of "sculpting in time" for almost an hour. How I wished at the time I'd had an editor handy!!