Why is "black noise" 1/(f^B) where B>2 associated with "persistence" and "long range dependence"? This book I'm reading uses the level of the Nile river as an example... I can understand what the Rescaled Range is saying but i don't get the implications w/respect to those terms or phrases. Is the idea that there is some relaxation process or processes with very long relaxation times? If so doesn't that somehow suggest one Nile flood is connected to another Nile flood by that process? This seems absurd, what process?