Today, an approximation became exact.

*Pi Approximation Day* was created on this day in 1988 by a physicist working in San Francisco. July 22 (22/7) is the common fractional approximation of pi though, actually, *every* expression of pi is an approximation, in that it’s an irrational number, so its value cannot be expressed exactly as a fraction, and its decimal representation never ends or repeats (it’s 3.1415926535 etc., and they’ve checked it to a zillion places without any change). It’s believed the ancient Egyptians and Indians knew it, and it appears explicitly in early Chinese and Greek texts.

Pi is the ratio of a circle’s circumference to its diameter, so it’s used extensively in the sciences, in architecture, even in art. It’s incredibly accurate — you need only take it out to 39 digits past the decimal point to make a circle the size of the observable universe accurate to the size of a hydrogen atom — but nevertheless it’s an imperfect description of the geometry of space. Designer Buckminster Fuller put it simply when he asked “Does Nature pause to calculate pi to infinity before it forms bubbles in the foam on waves as they crash onto the shore?” So pi isn’t a real answer, it’s just, well, as approximation. There’s even a movement underway now to replace our reliance on it with use of* tau*, which is the ratio of circumference to radius. Since tau is double pi, it’s also irrational, so it’s also not an ultimate answer.

So is math something that exists independently in the universe just waiting for us to discover its equations, or is it a model of our own creation?