Happy Pi Day! This year’s celebration of pi is even more exhilarating than most for math fans because the date as written in a MM/DD/YY format also represents the first five digits in the infinite string of numbers that make up pi – 3.1415 ... for 03/14/15.

It's the perfect opportunity to pause for a moment and appreciate just how much thought has been put toward calculating even those first five digits over the course of human history. Mathematicians have been trying to calculate the precise value of pi since ancient times. Its true value represents one of the most enduring searches in the field, which has left scholars stumped from their earliest attempts until today, when technology has largely taken over the task of defining pi.

Pi, most commonly expressed as 3.14, is a ratio that represents the relationship between a circle’s circumference and its diameter. Simply stated, the circumference of a circle of any size is about three times as much as its diameter. It’s an elegant relationship that lends a sense of orderliness to the world.

But it’s the “about three times” part that drives mathematicians mad. They would love to assign a precise value to pi. It would help improve the accuracy of calculations, surely, but more importantly, it would end a search that has spanned millennia and rendered pi one of the most elusive values in the field.

Perhaps the earliest estimation of pi was recorded in the scrawls of ancient Babylonians who wrote their rough calculations on a tablet and thought pi was about 3.125, according to the Exploratorium. Not long after, an Egyptian scribe named Ahmes offered up his best guess -- 3.1605 -- on a scrap of papyrus that is now housed in the British Museum.

A few centuries later, along came Archimedes. Fortunately for him, the Greeks had devised the Pythagorean theorem, which he used to make some clever calculations based on polygons sketched to fill up much of the space inside a circle (watch a video here). He came up with a range for the highest and lowest possible values of pi and made a best guess as to its exact value of 3.1418 – only a smidgen off. Not to be outdone, a Chinese fellow by the name of Zu Chongzhi did more of the heavy lifting by calculating pi out to six digits by hand, according to Gizmodo. It probably took him something like 1,000 tries, estimates the Confucius Institute.

Since then, mathematicians largely have been calculating pi to even more precise digits following the decimal point. Isaac Newton figured it out to 16 numbers. Others made it to 35 and then 100 digits – and then 527, as Gizmodo reports. The Greek letter that we recognize as pi -- π -- didn’t debut until much later, when a British mathematician named William Jones simply wrote it as such: 3.14159 = π and it stuck.

Nowadays, mathematicians are relying mostly on computers to crack pi's lengthy code. The machines are capable of rolling out billions of digits, and mathematicians have started combing through this data for any hint of a pattern that may help them to once and for all declare success in deciphering pi.

It’s safe to say that their efforts are far beyond all practical utility at this point – since only 39 decimal places would be needed to figure the circumference of a circle that would encapsulate the universe with a margin of error no greater than the width of a hydrogen atom, according to Rutgers. But if they knew the exact value, it might not be so much fun celebrating their search.

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