## Happy Pi Day, 2013

Today, March 14, is one of the days that is sometimes celebrated as “Pi Day”, in honor of the best-known irrational and transcendental number, the ratio of the circumference of a circle to its diameter, usually written as the Greek letter π (pi).  The date, 3/14, is chosen because the approximate value of π is 3.14159265…   Legend has it that the value was named π because pi is the first letter of the Greek word “περίμετρος”, meaning perimeter.

The New Scientist reports that this year, to observe Pi Day, Professor Marcus du Sautoy of the University of Oxford is sponsoring Pi Day Live, a project to “crowd source” the calculation of π (pi).  The value has, of course, alreay been calculated to trillions of decimal places; because it is an irrational number, it cannot be represented exactly by any finite decimal number.  (Pi is transcendental, also, of course.)  Pi Day Live is suggesting some relatively easy methods of getting an approximate value for π, including Buffon’s Needle.  I mentioned Buffon’s Needle in a Pi Day post back in 2010.  The New Scientist headline calls it an “ancient” method, which I think is a bit over the top for something described in the 18th century.

That earlier Pi Day post also tells a related story, of the Indiana state legislature’s attempt to set the value of pi by law, one of the all-time great accomplishments of legislative lunacy.

Finally, take a thought today for 134th anniversary of the birth of Albert Einstein.

##### Update Thursday, 14 March, 15:35 EDT

I’ve just noticed that there is a rendering error (at least in Firefox) on the “Find Pi” page I linked above.  The equation for the estimated value of pi is a bit garbled (where it reads 2L\over xp; the correct equation (using the “Find Pi” variable names) is:

$\pi = \dfrac {2 L}{x p}$

I’ve dropped the site a note with the correction.