pi, the ratio of the circumference of a circle to its diameter,
has been called "the world's most mysterious number"

its value is 3.1415926535897932384 . . . and thus far
it has been calculated to 1.24 trillion places to the right of
the decimal point, with no end in sight

this is amazing enough, but perhaps pi's most mysterious
quality is that it seems to pop up everywhere in physics
and mathematics

Wikipedia, for example, displays more than 50 formulas
containing pi - formulas that seem to have little relation to
geometry - for example,

the cosmological constant
    

Heisenberg's uncertainty principle
    

and Einstein's field equation of general relativity
    

the mysterious ubiquitousness of pi is the focus of the
video below



the soundtrack of the above is an excerpt from a
BBC Radio 4 5 Numbers podcast

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