Pi is the ratio of a circle's circumference to its diameter. If you take the circumference of any circle and divide it by its diameter, you will always get the constant value of Pi. It doesn’t matter if the circle is big, or if the circle is small. It just matters that the circle is a circle. Pi is usually written using the symbol p.
For years, mathematicians have been fascinated by p. p is an irrational number, which means that it cannot be expressed as the ratio of integer numbers. Because it is irrational, it's digits go on and on without any pattern. For years, mathematicians have tried to calculate more and more digits in p. Before computers were invented, less than 1000 digits in p had been calculated. But since the invention of computers, mathematicians started the race for calculating countlesss digits of p. The highest amount of digits ever created was 51 billion digits. Here are 100 of p's digits: 3.1415926535 8979323846 2643383279 5028841971 6939937510 5820974944 5923078164 0628620899 8628034825 3421170679.
p is the 16th letter of the Greek alphabet and is the most commonly recognized character. Suprizingly, the Greeks themselves did not use this symbol to represent the ratio of a circle's circumference to it's diameter. The symbol p has been used to signify this ratio during only the past 250 years.
