Today is Pi Day. Celebrated around the world every March 14th (3/14), the day focuses on the mathematical symbol that represents the constant ratio of a circle’s circumference to its diameter, approximated as 3.14159. This year’s Pi Day is a once-in-a-lifetime event; it will be 100 years until we experience 3/14/15 9:26:53 again – that’s pi to ten places!
Greek mathematician Archimedes devised the first recorded algorithm for calculating its value around 250 BC and, and as a result, pi is sometimes called “Archimedes’ constant”. Since the mid-18th century the Greek letter “π” has represented it, but the history behind the number is much deeper and well-rooted in the Middle East.
Some Egyptologists assert that the builders of the Great Pyramid at Giza had knowledge of π, as the ratio of its perimeter to its height closely reflects the proportions of a circle. This would place understanding of this irrational number as far back as 2589 BC.
The earliest written approximations of π are found in Egypt in the Rhind Papyrus, dated around 1650 BC, and in Babylon (now modern-day Iraq) on a clay tablet dated 1900–1600 BC, both within 1 percent of the true value. Two verses in the Hebrew Bible (written between the 8th and 3rd centuries BC) describe the dimensions of a ceremonial pool in the Temple of Solomon which implies knowledge of π.
It’s a day for mathematicians to get their geek on, with bake-offs, pi-eating contests, and slap-downs over who can recite more of its digits. Computers have calculated pi to more than a trillion digits beyond its decimal point, and the number continues infinitely without repetition because it is an irrational and transcendental number.
One of the most interesting celebrations of the number is a musical representation of pi, to 31 decimal places, at 157 beats per minute (which, incidentally, is 314 divided by two). Austin-based musician Michael John Blake produced the video, below, in 2011:
So how will you celebrate the 27th annual Pi Day (which, coincidentally, is also Albert Einstein’s birthday!).