Pi is an irrational number, meaning it has an infinite number of nonrepeating decimal places.
But it turns out, NASA scientists need only a small slice of pi — the first 15 decimal places — to solve most of their math problems. (And even when working out problems on the most mind-bending cosmic scales, they never need more than a few dozen extra digits!)
You may remember pi from school. It's the ratio between a circle's diameter (the distance between opposite points) and circumference (the distance around the edge). Simply put, pi is equal to the circumference of a circle divided by its diameter, which means you can figure out the circumference of any circle if you know its diameter or radius (half the diameter) and pi, which is most commonly abbreviated as 3.14 — which is why Pi Day is celebrated on March 14.
In the book (not the movie) "Contact" by Carl Sagan, we learn from the aliens that a secret message is hidden within one of the key transcendental numbers of mathematics! (PI)
The theological implications are intriguing (the whole universe must be constructed very carefully if one of its essential constants is in fact a coded message.)
Then, at the very end of the book, she sets her computer program -- the same one which first noticed the message from Vega -- to looking at the numerical expansions of Pi (in various different bases).She find a long string of 1's and 0's late in the expansion of Pi in base 11.
It's length is a product of two primes, indicating a two dimensional array.
So, she plots it on her computer screen (each digit representing a pixel) and sees a perfect circle.
The constant which describes the ratio of a circle's circumference to its diameter... contains a picture of a circle!
