Happy Pi Day!


Posted on behalf of Jeffery Baugus

This year’s Pi Day celebration will truly be a once-in-a-lifetime event! Each year, math enthusiasts and educators around the globe celebrate March 14th (3/14) as a time to teach about pi, the ratio of circumference to diameter on a circle. But in 2015, the digits of the date of Pi Day happen to fit the famous ratio even better – 3/14/15. Hardcore enthusiasts with have the height of their celebration occur specifically on Saturday, March 14, 2015 at 9:26:53 am (3.141592653…). The next time this same combination of numbers will occur will be in 100 years, in the year 2115.

Pi is quite possibly the most famous ratio in mathematics. The Greek letter pi, which is the equivalent of our letter “p”, was chosen in 1631 by William Oughtred to represent the ratio. In his book, Clavis Mathematicae, the symbol was related to the “periphery” of a circle (what we now call the circumference), which starts with the letter “p”. Pi is constant, meaning that any size circle will produce pi when its circumference is divided by its diameter. Pi is also an irrational number, meaning the number of decimal places it contains is infinite. The digits of pi do not repeat in a pattern, making the calculation of greater quantities of its digits a challenge. Mathematicians have been tackling this challenge for centuries.

Archimedes (c. 250 BC) used circumscribed and inscribed polygons with increasing numbers of sides (up to 96 sides) to approximate the circumference of a circle in an attempt to calculate pi more precisely. He concluded that pi was between 3 10/71 and 3 1/7 (3.140845…< ?< 3.142857…). Discovery Education’s Math Techbook contains an interactive that uses inscribed and circumscribed polygons to approximate pi.

Zu Chongzhi (c. 480 AD) increased the precision of the calculation of pi to 355/113 (3.1415929…). It is thought that to achieve this calculation, he must have started with a 24,576-gon and performed hundreds of complex calculations (without a calculator)!

Today, pi has been calculated to over 13,000,000,000,000 digits through the use of complex formulas and computer programs. Even with sophisticated technology, the calculations still take over half a year to complete!DETBM_PiDay_500x500

So what do you have planned for your students on Pi Day? Many teachers bring in pies, doughnuts, or other circular treats (Oatmeal Creme Pies are my favorite) for their classes. Some host recitation contests to see how many digits of pi their students can recite (my class record is 309 digits). Others host a series of arts and crafts activities for students. If you’re on the lookout for something unique for Pi Day this year, consider attending Discovery Education’s Virtual Pi Day Field Trip.

The virtual field trip took place today and featured a visit to the National Institute of Standards and Technology (NIST) to see how pi is being used every day to tackle problems worth solving. Highlights of the event included:

  • Fire Research Division: NIST engineers use computer models and then burn down actual buildings to develop standards for fire equipment, the size of crews, and fire fighting techniques.
  • Underground labs: There’s a reason NIST has labs located three stories underground. You will find out why and the kind of research that is being done.
  • The 3D Cave: Mathematicians and scientists use 3D glasses in a virtual reality lab to shrink down to the size of a rock and swim with flowing concrete.

The archive of the field trip is ideal for students in upper elementary, middle and high school classes. Visit http://www.discoveryeducation.com/PiDay to watch the archive and use it to help celebrate Pi Day in your classroom and learn real-life applications of math!