Air traffic control (ATC) is a service provided by ground-based controllers who direct aircraft on the ground and through controlled airspace, and can provide advisory services to aircraft in non-controlled airspace.
While the genre of some works of literature can be debated, Macbeth written by William Shakespeare seems to fit into a perfect mold. Aristotleâs definition of a tragedy, combining seven elements that he believes make the genre of a work a tragedy, is that mold. Displaying all seven aspects, Macbeth fits the definition precisely. Key elements in the play substantiate the fact that Macbeth is a serious story, the first elements of Aristotleâs definition.
The four elements: c.450 BC. 1  The Greek philosopher Empedocles, a native of Sicily, introduces a theory which will be accepted in Europe until the 17th century. He states that all matter is made up, in differing proportions, of four elemental substances - earth, air, fire and water.