March 14th marks Pi Day, an annual celebration of the mathematical sign pi. March 14th was selected because the numerical date (3.14) represents the first three digits of pi.

## An engineering essential

In mathematics, pi is crucial because of what it represents in relation to a circle — itโs the constant ratio of a circleโs circumference to its diameter. Pi is essential to engineering, making modern construction possible.

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The importance of pi (ฯ) has been known for almost 4000 years. But since itโs an infinite number, mathematicians are only able to approximate its actual value. The earliest recorded use of pi dates back to 1900 BCE in ancient Babylon. A Babylonian tablet indicates their estimation for the value was 3.125.

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But thereโs a rather large piece of evidence that civilizations were aware of the importance of pi even earlier. The Great Pyramid of Giza, built between 2550 and 2500 BCE, has a perimeter of 1760 cubits and a height of 280 cubits, which gives it a ratio of 1760/280 — approximately 2 times pi.

## Refining the estimation

While earlier mathematicians were able to approximate pi to a fairly close decimal, the Ancient Greek mathematician Archimedes is most commonly credited with being the first to accurately calculate its estimated value.

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Using the Pythagorean Theorem to find the areas of polygons, Archimedes was able to demonstrate that the value of pi was between 3 10/71 (3.1408) and 3 1/7 (3.1428).

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Since Archimedesโ discovery in the third century BCE, the value of pi has been calculated to more than 1 trillion decimal places. However, for the purpose of problem-solving, the first three digits (3.14) or the fraction 22/7, are commonly accepted as accurate estimations.

## How to celebrate Pi Day

If youโd like to show your true dedication to pi, you could try to memorize as many digits as possible. But the record is a tough one to beat. On March 21st, 2015 Rajveer Meena of India set the world record for the most decimal places of pi memorized, reciting 70,000 digits. Rajveer wore a blindfold during the entire recall, which took nearly 10 hours.

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For a less time-consuming celebration, you could purchase a bottle of Pi by Givenchy, a cologne thatโs marketed to be โfor a man who aims to exceed his own limits.โ

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And if you prefer to batch your celebrations, you can also throw in a birthday party for Albert Einstein. As one of the most influential mathematicians and physicists in history, itโs fitting that Einstein was born on March 14th, 1879, just over a century before Pi Day was founded.