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by anguilla on June 1st, 2004
Pi is the ratio of the circumference of a circle to its diameter. To put it another way, it's the length of the circumference divided by the length of the diameter.
Pi always works out to be the same value, no matter what size the circle is. So Pi is a Big Deal because it lets you easily measure the length of the curved line that makes up a circle.
Pi = C/D, so if you know the diameter and Pi, you can calculate the circumference.
IF you do the math, and divide the circumference by the diameter, you'll get 3.14159265358979323846264338327950288419716939937510.....
-- where the dots represent the fact that no matter how long you keep dividing, it never comes out even and the pattern of numbers doesn't repeat. It has reportedly been calculated out to 206 billion digits!!
There are charts that describe the history of Pi, which goes back to the Babylonians (2000 BC), and how accurately (or inaccurately) Pi has been calculated through the years. I'm sorry I can't make it appear in neat columns here, but you can see it neatly if you go to http://www-gap.dcs.st-and.ac.uk/~history/HistTopics/Pi_chronology.html
Even though the rough value of Pi was known long before his time, the first theoretical calculation seems to have been carried out by Archimedes of Syracuse (287-212 BC).
---http://www-gap.dcs.st-and.ac.uk/~history/HistTopics/Pi_through_the_ages.html
I have altered the answer in response to comments from readers. Sorry for any mistakes.
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Comments
Thorough answer.
by Andy Is Wicked Married to Penal Colony on June 13th, 2004
Actually, 22/7 is 3 1/7, which is 3.142857142857142857... Pi is a much more irrational number.
by DeuceOfSpades on June 29th, 2004
by Quirkie on September 16th, 2005
this is what I was searching for.
by Akshay Agarwal on March 7th, 2005
Very unhelpful reference to 22/7
by Les Toth on March 15th, 2005