On **Tuesday, March 14** have a pizza – or maybe an apple “pie” to **celebrate “Pi” day**!

**3.14. “Pi”.** The number** π **is the mathematical constant, representing the ratio of a circle's circumference to its diameter. It has been represented by the Greek letter “π” since the mid-18th century, though it is also sometimes spelled out as** “Pi.”**

**Pi** is an irrational number and cannot be expressed exactly as a common fraction, although fractions such as 22/7 and other rational numbers are commonly used to approximate π. Its decimal representation never ends and never settles into a permanent repeating pattern. The digits appear to be randomly distributed; however, to date, no proof of this has been discovered. The decimal representation of π as of late 2013 has been calculated to over 13.3 trillion digits. Attempts by individuals to memorize the value of π with increasing precision have led to records of over 67,000 digits! Click here to see π calculated to 1,000,000 digits.

According to PC World, the earliest textual evidence of pi dates back to 1900 BC. The Babylonians and the Egyptians both had a rough idea of the number. The Babylonians estimated Pi to be about 25/8 (3.125), while the Egyptians estimated it to be about 256/81 (roughly 3.16). The Ancient Greek mathematician Archimedes of Syracuse (287-212 BC) was probably the first to calculate an accurate estimate of the value of Pi. In 1707, Welsh mathematician William Jones was the first to use the Greek letter Pi (π) but it wasn't until 1737 that Swiss mathematician and physicist Leonhard Euler popularized the use of the symbol. The π symbol was taken from the Greek word for “perimeter.”

**“Pi Day” **as a cause célèbre dates to the late 1980’s. **Pi Day **appears to have been conceived in 1988 by physicist Larry Shawn of San Francisco’s Exploratorium science museum. In an expression of the “small world syndrome” Albert Einstein was born on “Pi Day” in 1879.

In March, 2009, The House of Representatives first “support[ed] the designation of a “Pi Day” and its celebration around the world”.

To learn more go to PiDay.org.

**Article by:****W. Jerrold Samford**, Environmental Compliance Specialist, Troutman Sanders

**Video** courtesy of the Science Museum of Virginia: