People celebrate today as “π day“, an official designation in the US^{*}

3.141592653589793238462643383279502

88419716939937510582097494459230781

64062862089986280348253421170679821

48086513282306647093844609550582231

72535940812848111745028410270193852

110555964462294895493038196...5...

Do you know how we know those digits? If you’d like to find out, I’ve written a blog post over at Second-Rate Minds: “How to calculate π“.

* This is not necessarily the best day. “3.14” is a very crude approximation for π and translating 14th March into this number requires a month/day dating system. 22/7 gives 22nd July in day/month format and gives a slightly closer approximation for π: 3.142857… (3.14 is π-0.00159…, while 22/7 is π+0.00126…). Having said that, 14th March has the tantalising prospect of 1:59 and 2.65359… seconds giving an actual value of π… Perhaps we need a fourteenth month…