From the mythology of night time and darkness, to being rebellious and cool, to a word which has come to define a race of people, black, as a colour and a concept, has always meant many things. Why? Where do positive and negative ideas that have been associated with black come from, how much resonance do they still hold today? Mike Williams peers into the world of black, its science, history, psychology and politics and asks why black has so many different meanings.(Image of black and white grid, BBC Copyright)