# Here’s your primer on Pi Day!

*It’s Pi Day! And, we’re not talking about the dessert (but that’s worth celebrating, too). This Pi Day has to do with mathematical ratios — and it also happens to be a famous scientist’s birthday. Both are right in STEM’s wheelhouse, and both are worth noting. What’s a teacher to do to mark the dual occasions? We asked Julie Medina, school programs manager at the Fleet Science Center in San Diego, California, to suggest activities for different age groups. And, she also gave us the complete lowdown on pi:*

**Q: Tell us about Pi Day, its history and what it celebrates.**

A: Pi Day was founded by physicist Larry Shaw in 1988, and it’s a celebration of the number pi, which is approximately 3.14159. The first three digits (3.14) are the reason for celebrating on March 14 (3/14).

Pi (Greek letter “π”) is the mathematical symbol used to represent the ratio of the circumference of a circle (the line bounding the circle) to its diameter (the line passing through the center of the circle from one side to the other).

March 14 also happens to be Albert Einstein’s birthday, so it is a perfect day to celebrate math and science.

**Q: Can you tell us some fun facts about pi?**

A: You can take any circle and divide the circumference by the diameter, and the result should equal approximately 3.14159 (depending on the accuracy of your measurement). Regardless of the circle’s size, this ratio will always equal pi.

Pi has been calculated to more than one trillion digits beyond its decimal point, which makes it a great number to incorporate for a variety of age groups.

**Q: Can you share some STEM-related activities that elementary school educators — both in-class and after-school — can use to get their students interested in Pi Day?**

A: A great way to start off any discussion of pi with grades 3 and higher is to measure circles and divide by the diameter.

For this activity, find any circular object in the classroom. Take a piece of string, and place it exactly once around the circle, then straighten out the string and measure it. This distance is called the circumference of the circle.

Next, measure the diameter of the circle, or the length straight across the circle, from one side to the other, making sure to go through the center.

If you divide the circumference of the circle by the diameter, you will get approximately 3.14, no matter which circle object you chose to measure. It seems to be a magic trick!

For even younger students, you can take that string measuring the circumference and show that if you fold it in three, it almost exactly matches the distance straight across the circle.

**Q: For middle and high school students, what STEM activities would you recommend?**

A: Because older students understand more extensive decimals, these students could do more advanced and accurate calculations of the circumference of things that are very large or very small. These students could also compete to memorize and recite the most place values of pi.

Circle bingo is another great option in which you use bingo cards with numerical answers and prompts that require students to find the radius, diameter, circumference or area of a circle. Older students could also use pi to calculate and compare the sizes of planets in our solar system.

**Q: Are there other real-life applications that help to show why knowing about pi is useful?**

A: Absolutely! Anybody who has ever purchased a fitted hat has used the number pi, whether they realized it or not. You can measure your own hat size by wrapping a measuring tape around your head and then dividing that measurement by pi. The resulting number is your fitted hat size! Most hat sizes range between 6 and 8.

Another interesting way to think about circles is their connection to cycles. Rhythmic motions all encounter pi — in waves, orbits, earthquakes, heartbeats, music, periods of wakefulness and sleep, and so much more. Wherever there is a motion that is repetitive, pi will underlie the mathematics.

One more interesting use for pi in everyday life is navigation systems and positioning such using a GPS. To determine your location on our spherical planet, pi must be used.

**Q: The Fleet is a science center. Do you mostly celebrate math on Pi Day, or are there science concepts that relate?**

A: Well, we certainly celebrate the number pi — for example, we have a Pi Day event for teachers on March 14 that is part of our ongoing teacher programming.

But, we also celebrate Einstein’s birthday that day, with “Flat Albert” activities requiring people to print out a picture of Einstein and then photograph him in crazy places. This is a great activity for discussions on perspective because you can place the picture of Einstein closer or farther from the camera, making him look larger or smaller, compared with other objects in the view.

We also worked with teachers to create gravity well to use with their students to explore Einstein’s theory of relativity.

While our Pi Day workshop is not one that we publicize year-round for schools, it actually can be requested at any time of year.

**Q: If a teacher is working on a STEAM unit, are there art activities that relate to pi?**

Q: If the students are already familiar with making bar graphs, have them create a bar graph with each bar representing a digit of pi. This can either be done by coloring in squares on a piece of graph paper or gluing squares onto a larger piece of paper.

You can create any type of background (a sunset or starry night sky are popular choices), and then the bar graph ends up looking like a cityscape with many skyscrapers. There is also the possibility of using small, colored circles to create a larger image, almost like a mosaic.

**Q: In general, do you have tips for teachers about tackling such hands-on activities in the classroom?**

A: I’m a big advocate for linking an activity to something students will also hear about in the news or in social media. If their interest is already piqued, then it makes the lesson something they already want to learn more about.

Many times, we’re able to incorporate hands-on elements using things that are readily available in a home or classroom. By incorporating hands-on components, we have the opportunity to make learning fun, and to appeal to a variety of different learning styles.

We find that additional inspiration and problem-solving abilities result if the hands-on component can also incorporate elements of inquiry and discovery, in which the student determines the question he or she is trying to investigate.

*Editor’s note: Thank you to Vince Stewart, the Executive Director of the California STEM Network for connecting us with the Fleet Science Center. California is a member of STEMx. *