March 14, when written as 3.14, is the first three numbers of pi (π). To commemorate the (completely artificial) confluence of the world’s most famous and never-ending mathematical constant with the way we can write the date, math enthusiasts around the country embrace their inner nerdiness by celebrating π, the ratio of the circumference of a circle and its diameter.

The date–which also happens to be Einstein’s birthday–inspires celebrations every year. Today. the Massachusetts Institute of Technology is posting password-protected decision letters on its admissions office site–would-be attendees can view whether they gained admittance at 6:28 pm (approximately equal to 2π, or the ratio of a circle’s circumference to its radius). Not to be outdone, Princeton’s celebrations of pi span an entire week, complete with a pie eating contest, an Einstein look-alike contest and a π-themed video contest (videos extolling pi and Einstein’s birthday must be less than 3.14 minutes; the winner will be announced at 3:14 today and will receive–you guessed it–$314.15).

Just why are people crazy about pi? The number–three followed by a ceaseless string of numbers after the decimal point, all randomly distributed–is the world’s most famous irrational number, meaning that it cannot be expressed as through the division of two whole numbers. In fact, it is a transcendental number, a term which boils down the idea that it isn’t the square root, cube root or nth root of any rational number. And this irrationality and transcendental nature of pi appeals, perhaps because pi’s continuous flow of numbers reflects the unending circle it helps to trace.

Pi has held an almost mystical quality to humans throughout time. Its unspoken presence can be felt in the circular ruins of Stonehenge, in the vaulted ceilings of domed Roman temples, in the celestial spheres of Plato and Ptolemy. It has inspired centuries of mathematical puzzles and some of humanity’s most iconic artwork. People spend years of their lives attempting to memorize its digits–they hold contests to see who knows the most numbers after the decimal, write poems–”piems,” if you will–where the number of letters in each word represents the next digit of pi, compose haikus (pikus)…the list goes on and on like pi itself.

**Here are some notable moments in the history of pi:**

**1900-1650 BC**: A Babylonian tablet gives a value of 3.125 for pi, which isn’t bad! In another document, the Rhind Mathematical Papyrus, an ancient Egyptian scribe writes, in 1650 BC “Cut off 1/9 of a diameter and construct a square upon the remainder; this has the same area as the circle” This implies that pi is 3.16049, “which is also fairly accurate,” according to David Wilson of Rutgers University’s math department.

**800-200 BC:** Passages in the Bible describe a ceremonial pool in the Temple of Solomon: “He made the Sea of cast metal, circular in shape, measuring ten cubits from rim to rim and five cubits high. It took a line of thirty cubits to measure around it” (I Kings 7:23-26). This puts pi at a mere 3.

**250 BC:** Archimedes of Syracuse approximates the area of a circle by using the Pythagorean Theorem to find the areas of two shapes–a 96-sided polygon inscribed within the circle and an equally faceted polygon within which the circle was circumscribed. The areas of the 96-sided shapes sandwiched the area of circle, giving Archimedes upper and lower bounds for the circle’s extent. Though he knew that he had not found the exact value of pi, he was able to approximate it to between 3 1/7 and 3 10/71.

**Late 1300s**: Indian mathematician and astronomer Madhava of Sangamagrama first posits the idea that pi could be represented as the sum of terms in an infinite sequence–for example, 4 – 4/3 + 4/5 – 4/7 + 4/9…His work helped inspire branch of mathematics that examines the results of mathematical operations performed over and over on a never-ending stretch of numbers.

**1706:** Welsh mathematician William Jones began to use π as a the symbol for the ratio of the circumference of a circle to its diameter. Famed Swiss mathematician Leonhard Euler adopted this usage in 1737, helping to popularize it through his works.

**1873**: Amateur English mathematician William Shanks calculates pi out to 707 digits–his number was written on the wall of a circular room–appropriately named the Pi Room–in the Palais de la Découverte, a French science museum. But his number was only correct to the 527th digit–in 1946, the error was finally caught, and in 1949, the number was corrected.

**1897**: Lawmakers in Indiana almost pass a bill that erroneously labels the value of pi to 3.2. Cajoled by an amateur mathematician Edwin Goodwin, the Indiana General Assembly introduced House Bill 246, which introduced “a new mathematical truth” for sole use by the state. The “truth” was an attempt to square the circle–a puzzle which requires that a circle and square of the same area be constructed using only a geometrical compass and a straightedge. The bill unanimously passed the house, but the senate and hence the state was spared from embarrassment by C.A. Waldo, a Purdue mathematics professor who coincidentally happened to be in the State House that day. “Shown the bill and offered an introduction to the genius whose theory it was, Waldo declined, saying he already knew enough crazy people,” Tony Long of *Wired* wrote. Waldo gave the senators a math lesson, and the bill died.

**1988**: Larry Shaw of San Francisco’s Exploratorium inaugurates the first Pi Day celebration. This year, even as it prepares for its grand re-opening in April, the museum holds its 25th annual Pi Day extravaganza.

**2005**: Chao Lu, then a graduate student in China, becomes the Guinness record holder for reciting digits of pi–he recited the number to 67,980 digits. The feat took him 24 hours and 4 minutes (contest rules required that no more than 15 seconds could pass between any two numbers).

**2009**: Pi Day becomes official! Democratic Congressman Bart Gordon of Tennessee’s 6th congressional district, along with 15 co-sponsors, introduced HR 224, which “supports the designation of a Pi Day and its celebration around the world, recognizes the continuing importance of National Science Foundation math and science education programs, and encourages schools and educators to observe the day with appropriate activities that teach students about Pi and engage them about the study of mathematics.” The resolution was approved by the House of Representatives on March 12 of that year, proving that a love of pi is non-partisan.

How are you celebrating Pi Day?

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