# Today is pi day

[mathematics

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Amazing!

Today is pi day</div> <div style="margin-bottom: 0.5em;">via kottke.org by Jason Kottke on 3/14/11.

And in celebration, this is my new favorite fact about pi: we have calculated pi out to over 6.4 billion digits but only 39 of them are needed to calculate the circumference of a circle as big as the universe “with a precision comparable to the radius of a hydrogen atom”. (via @santheo)