From what leads from point A to point B, to the GPS system, there is only one number that makes these and many other innovations possible. It is the number Pi, 3.14159, which has proven to have become an irreplaceable part of everyday life.

Pi is so famous that he even has his own day of celebration,**Pi Day, which is honored each year on March 14.**

What is it about pi that draws so much attention and that even invites such a celebration? Simply put, pi is one of the oldest and most widely used mathematical constants known to mankind.

**Nearly 4,000 years ago, the ancient Babylonians and Egyptians observed that the ratio of a circle’s circumference to its diameter was the same constant for each circle.**And even though early estimates of this constant were somewhat inaccurate, the Babylonians and Egyptians were among the first humans to show that pi could be used to calculate the area of a circle.

From what point in history do the most accurate calculations of pi come? We have to go back to ancient Greece and the famous Greek philosopher**Archimedes**in 200 BC and also, later, to the Chinese mathematician Zu Chongzhi in the 5th century. Mathematicians around the world continued to delve into the meaning of pi over the next several centuries.

In the early 18th century, in the early 1700s, mathematicians William Jones and Leonhard Euler popularized the use of Pi to represent this enigmatic mathematical constant. In 1767, the also mathematician Johann Heinrich Lambert was the first to realize that the number pi was irrational, that is, that it was a number that could not be expressed as the exact quotient of two whole numbers. (It is not a number of the type π = p / q in the style of 355/113 (although it is a good approximation)

So things,**Lambert helped give birth to the nature of pi as we know it today.**

Currently, the number Pi is fundamental to all the disciplines of science and engineering that exist: it is used in signal processing for radio or television; mechanical engineers use pi to design and build airplanes, automobiles, and other heavy machinery; statisticians use pi to make sense of large data sets, and so on.