## Thursday, September 2, 2010

### Rhymes help to remember the digits of Pi

Calculated at the website, WolframAlpha, here are the first fifty-nine digits of the irrational number π (ratio of a circle's circumference to its diameter):

π = 3.1415926535897932384626433832795028841971693993751058209749...

Before computers became available  to calculate π to lots of decimal places in an instant, people who did scientific calculations could keep the number easily available by memorizing some of the digits.  The website fun-with-words offers several mnemonics for  π , the most common type being a word-length mnemonic in which the number of letters in each word corresponds to a digit. For example the sentence, "How I wish I could calculate pi," gives us the first seven digits.

This brief stanza gives thirteen digits of π:

See, I have a rhyme assisting
my feeble brain,

The first twenty-one digits are shown by this rhyme:

Now, I wish I could recollect pi.
"Eureka," cried the great inventor.
Christmas Pudding; Christmas Pie
Is the problem's very center.

To remember thirty-one digits of π, one may use these lines:

Sir, I bear a rhyme excelling
In mystic force, and magic spelling
Celestial sprites elucidate
All my own striving can't relate
Or locate they who can cogitate
And so finally terminate.
Finis.

Wikipedia and numerous other online sources offer variations of these and more.  One of the most amazing mnemonics is  "Near a Raven" --a variation by Mike Keith of Edgar Allen Poe's well-known poem that encodes the first 740 digits of π.  To represent  the digit zero (which does not occur in π until the thirty-second place) a ten-letter word commonly is used.

Previous 2010 blog postings with poetic references to π include August 23, August 18, June 7, May 12, April 26, and April 19.