In brief, it contrasts the modern understanding of causality (and the mathematics this presupposes) with the more recent, perhaps in a sense "postmodern" understanding of causality (again with a concomitant mathematical model) and on the basis of this distinction, draws some interesting parallels between economics and natural events.
"π has fascinated mathematicians, engineers and other people for centuries. It is a mathematical constant that is the ratio of a circle's circumference (C) to its diameter (d); This also explains why and how this number got its name: the lowercase π was first adopted in 1706 as an abbreviation for this number because it is the first letter of the Greek for "perimeter", specifically of a circle." Introduces a video by Numberphile explaining more about the determination of π