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As a baker with six too many university mathematics courses behind me (only three of those made me cry), Pi Day is one day of the year that would be blasphemy to forget. A couple years ago was the coolest Pi Day of the century: The first five digits of pi are 3.1415… the date was March (**3**^{rd} month) **14**^{th}, 20**15.** While this year’s Pi Day wasn’t quite as awesome, it’s still a fantastic day to celebrate both mathematics and baking. (Incidentally, it also happens to be Albert Einstein’s birthday.)

Pi is an irrational, and infinitely long value – its decimal places never repeat itself in a pattern, and it never ends. (Here’s pi to 100,000 decimal places [1] and to 1 million [2].) It has been calculated to several trillion decimal places, but one source states that only 39 decimal places are needed to calculate the circumference of the visible universe [3].

The history of pi extends back to ancient times, when scholars of various cultures attempted to calculate pi. Biblical approximations put the value of pi at 3. Babylonians estimated 3+ 1/8 (=3.125), while the Egyptians thought it was 2^{8}/3^{4} (=3.1605…). Of all the incorrect values of pi, the Greeks were the closest to the actual value, with 22/7 (=3.1428). Only the Chinese managed to calculate the first 6 (accurate) decimal places of pi (3.141592) [4].

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The history of pie starts at a similar time to that of pi. Ancient civilizations developed the first forms of pie and pie pastry, of which Greek and Roman bakers produced the first products that fit into a recognizable definition of pie. Using fat (likely olive oil), water, and flour, they made a pastry shell which surrounded a meat dish. A more modern version of pie was developed in the Middle Ages, along with the origins of the modern name, ‘pie’. The Oxford English Dictionary suggests that it was “Middle English: probably the same word as pie, the various combinations of ingredients being compared to objects randomly collected by a magpie” [5]. Substituting lard for the olive oil used by the ancients, pie crust was used as a dish in which to cook other savoury or sweet items. The first forms of lighter pastry dough appeared first in the 17^{th} century, with short paste, and puff paste [6]. Sweet pie varieties, however, did not become popular until 200 years later. In the span of 150 years, from approximately 1800 until the mid-20^{th} century, sweet pie varieties increased from 8 recorded recipes to 65 [7].

Regardless of whether you prefer pi or pie, there are a ton of cool ways to celebrate Pi Day – even NASA and the American Mathematical Society join in the festivities [8] [9]. And now, in honour of this sweet holiday, it’s time to bake some pi themed pie (or plan ahead for next year, since I’m a few days late now… oops).

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