'Tau day' marked by opponents of maths constant pi

The mathematical constant pi is under threat from a group of detractors who will be marking "Tau Day" on Tuesday.

Tau Day revellers suggest a constant called tau should take its place: twice as large as pi, or about 6.28 - hence the 28 June celebration.

I guess it'll be 'simpler' to calculate circumferences using τr rather than 2πr...