Science City at the Tucson Festival of Books will celebrate a milestone: Super Pi Day.

π — also known as pi — is a numerical constant, which simply means it is a number that never changes.

Its value is defined, and has been since Egyptians and Babylonians first estimated it back around 1900-1600 BC. Since then, its decimal approximation length has reached 3 trillion units. There was even one man from China who memorized the first 67,890 digits and recited them without error. (Others claimed to have done more, but weren’t officially verified.)

When you think “pi,” most people think about how it is used to calculate the area of a circle or volume of a spherical or cylindrical object. What you may not know is pi extends far beyond geometry.

Pi is used often in mathematics, but in many other disciplines as well. For example, when an ophthalmologist is studying the human eye and how it works, pi is often utilized in his or her calculations. And when biochemists are studying the double helix of DNA, they see pi at work as well.

What about in your every day life? Pi is being used whenever you use a navigation system to calculate global positioning. Many things you use every day — like your watch, your car, or almost any form of electricity — all work properly because someone used pi to make accurate calculations.

Even the rainbow follows the numeric values of pi.

The expansion of pi is 3.141592653…

This makes 2015 a unique year for Pi Day (and Albert Einstein’s birthday), which is celebrated on March 14. It is Super Pi Day – 3.14.15.

To celebrate this milestone, the book fest’s Science City will have a Science of Pi tent. It will have all sorts of fun ways to explore the incredible and versatile pi.

Experience Buffon’s Needles, a hands-on way to estimate pi using just toothpicks and parallel lines. You can also make a visual representation of pi with colors and compete in our own contest to see how many digits of pi you have memorized. (So start brushing up on those digits now!)

Keep your eye out for special events happening at 9:26 a.m. and 9:26 p.m. to celebrate Super Pi time – 3.14.15 at 9:26.

Join us at Science City on March 14-15 so we can show you why we are obsessed with science (and pi).

Jennifer Sedler is assistant director of the STEMAZing Project, office of the Pima County School Superintendent, a Science City partner/participant.