American π

3.142 .. and so on, forever - the ratio of the diameter of a circle to it's circumference, or π (pi).  We were plagued by this little chap at school, or we revelled in it, in the strange inexplicable precision of a number which never has an end.

These musings are inspired by Marcus du Sautoy's Sexy Maths article in a recent edition of The Times.  He talks about a whole range of pi things, noting that today is pi day, when mathematicians eat lots of pies to celebrate!  The article is quite fun, talking about the importance of pi in mathematics, but also about odd ways to calculate pi - including throwing a needle on to a sheet of paper where the lines are separated by the length of the needle (the proportion of times the needle ends lying across a line is 2 divided by pi).  But he also tells you that we (you? me?) know the value of pi to a trillion digits - and what use is that exactly, when a mere 39 digits is enough to calculate the circumference of the visible universe to the accuracy of a single hydrogen atom?

And why "American" pi in my title?  Well apart from the bad cinematic reference, the day for celebrating pi is taken from the first three digits of the number itself, so March 14.  In England, it would have been the third of the fourteenth month (oops), or the 31 April (oops again).  Curiously, mathematicians use this day to celebrate, but engineers - who du Sautoy says don't care about accuracy so much (?) use 22 July, after the fraction 22/7, a workaday substitute for pi in basic calculations.

Comments

[glo]

I am glad I now know there is a pi Day! But to tell the truth, I am sick of this trend of celebrating everything all over the year, it's hapless and pi tiful - sorry!

To my favourite Cat
I just want to say hello to Dark Puss. What you wrote the other day was just unbearably cute! I made me melt instantaneously and I almost ran at my local vet to get my own cat!

"However I borrowed Kafka on the Shore instead (the cute black kitten on the cover got the better of me). I must say I am not disappointed in the Murakami, and the concept of a flute made from the souls of murdered cats is an intriguing and disturbing one, especially for me."
It was here:
http://booksdofurnisharoom.typepad.com/books_do_furnish_a_room/2009/02/bang-bang-bang-goes-the-farmers-gun.html#comments
A big, big hug to the lovely feline!

[Dark Puss]

Calculating the value of pi to an enormous number of digits is not only interesting from a number theoretic point of view but is a good test of state-of-the-art supercomputers. Readers may be interested in this page http://mathworld.wolfram.com/PiDigits.html from Wolfram which contains some interesting information on some of the statistical properties ("randomness") of the digits of pi. Readers with a reasonable background in mathematics may be fascinated by the number of formula relating to pi that are listed here http://mathworld.wolfram.com/PiFormulas.html . Some of these are due to the Indian mathematician Ramanujan about whom Cornflower posted a weblog recently here http://www.cornflowerbooks.co.uk/2009/02/hard-sums.html Enjoy!