# Today is Pi Day, we tell you why

**The circle and other round shapes have been used by humans around the world for thousands of years.**From the manufacture of stone tools in the Stone Age to the invention of the wheel in the Bronze Age.

The circle is a symbol of perfection and was essential in the manufacture of a variety of things.

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What makes a circle particularly remarkable is that no matter its size, the length of its circumference (the edge of the circle) and its diameter are invariably proportional. This mathematical constant, which we still do not know with absolute accuracy, is known as **The number pi (p) and is mentioned frequently in different contexts.**

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Although the Greek letter pi was introduced as an official designation in the 17th century by a British mathematician **William asked**Inspired by the proto-words “circumference” and “circumference”, the search for an increasingly precise value for this famous constant has been a mathematical obsession for thousands of years, in various cultures. Pi is an irrational number, which means that it cannot be expressed as an exact fraction and that decimals do not repeat in a pattern. Although a challenge faced by some of the most famous mathematicians in history, **Knowing a more precise value for pi has important implications in fields in which it is ubiquitous**Such as engineering, statistics, cryptography, and computer science, to name a few.

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In the ancient Egyptian civilization, the approximate value of pi was 3160, while in Mesopotamia it was 3125. One of the first mathematicians who a**Try to calculate pi with greater accuracy was Archimedes**, which used the inscribed (inside) and bounded (outer) polygons of a circle to find the value of the sum of its sides. Then he geometrically calculated the distance from end to end of the polygon, which is much like the diameter of a circle. The more sides a polygon has, the more accurate the value of pi. Using 96-sided polygons, he was able to constrain the value of pi between 3.1408 and 3.1429 in the third century BC. c.

Throughout history, closer and closer to the exact value of pi has been achieved, and many mathematicians have made significant contributions. For example, the astronomer Ptolemy calculated the value of 3.14166 using a 120-sided polygon, while the Chinese mathematician **Zu Chongzhi’s value has reached 3.1415937**. This value was not exceeded until the fifteenth century, a thousand years later.

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However, the most important advance in calculating pi occurred in the 20th century, thanks to the computer revolution. The first computer that was used to calculate its value was the Eniac, a gigantic machine that took up an entire room under the direction of the eminent mathematician **John von Neumann **in 1949, and after nearly 70 hours of processing. By 1966, 250,000 decimal places of pi were already known.

Today, progress in calculating decimal places of pi continues by leaps and bounds. **In 2019, during Pi Day, Emma Haruyka Iwao, a computer scientist and Googler, announced the discovery of more than 31 trillion decimal places for pi,** Exactly 31’415.926’535.897. Every year, the third month of the calendar and the fourteenth day, remembering the approximate value of 3.14 of the number pi, the day of Pi is celebrated and **International Maths Day**, respectively. The latter, under the slogan “Mathematics for All”, seeks to promote inclusion and equitable access to education in this field.

Today is a special and symbolic day, a round day, because it reminds us of the close relationship between the circle and the most famous and elusive mathematical constant: pi. In addition, it gives us the opportunity to highlight the presence of mathematics in all areas of our daily lives. To complete the celebration, the day also marks the birth of one of the most important scientists in history, Albert Einstein, who was born on March 14, 1879. Happy Pi Day!

Santiago Vargas

PhD in Astrophysics

Astronomical Observatory of the National University

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