# 20 Fascinating Facts Behind the Mystery of Pi

## Find out why this ancient mathematical constant gets an annual celebration—one that’s growing every year!

## Pi has many real-world uses

It’s not all fun and games and feats of memory: Scientists use pi every day to make important calculations, such as determining the volume of a sphere, the area of a circle, and the volume of a cylinder. “Those relationships form the basis for how stiff a structure is, how it will vibrate, and understanding how a design might fail,” says Charles Dandino, an engineer at the Jet Propulsion Lab. “In my career, pi has allowed me to calculate the size of a shield needed to enter the atmosphere of Venus and the size of a parachute that could safely land the Curiosity rover on the surface of Mars,” says another JPL engineer, Anita Sengupta. Another handy tool that makes use of pi? The GPS system in your car and smartphone use it to calculate specific locations on Earth.

## Do a magic trick to calculate pi

To try this easy activity known as Buffon’s Needles, you need a large sheet of paper, at least 30 toothpicks, a ruler, and a pen. Using a toothpick to determine the distance between them, draw a series of parallel lines on your paper. Then throw the toothpicks onto the paper at random.

Next, take away any toothpicks that are only partially on the paper, or that didn’t land on the paper at all. Count how many are left on the paper. Also, count how many cross a line.

Divide the total number of toothpicks by the line-crossing toothpicks. Now multiply by two, and you should get pi! Check out these other brain-boosters you can do with your kids.

## Pi is a movie star

Pi has made several significant appearances in pop culture. Most notably, there is an entire film about it, called *Pi: Finding Faith in Chaos.* The 1998 film, which won an Independent Spirit Award for screenwriter Darren Aronofsky, is admittedly a bit of a downer, as it follows a tormented mathematician trying (and failing) to work out the secrets of the universe. In the Sandra Bullock thriller *The Net*, clicking on a pi symbol is what sends Bullock’s character into the confidential government files, and in Alfred Hitchcock’s *Torn Curtain*, the pi symbol is the code that represents the escape network. It’s even vanquished TV villains; in a *Star Trek *episode, Spock outsmarts an evil computer by challenging it to calculate the final digit of pi.

## A pi-themed crop circle left scientists scratching their heads

In 2008, a 150-diameter crop circle suddenly appeared by Barbury Castle, near the English village of Wroughton. Researchers and conspiracy theorists puzzled over its origin and meaning, and an astrophysicist eventually figured out that the image was a code representing the first ten digits of pi. Learn about some of the most baffling unsolved mysteries about the universe.

## Pi makes people laugh

As it’s a monosyllabic word that also happens to sound exactly like a yummy dessert, there’s no shortage of jokes and puns to be made about pi. “What kind of reptile do math teachers keep as pets?” “Pi-thons!” “Why should you never start a conversation with pi?” “Because it goes on forever!” A comedian named John Evans even used a pi-themed joke in one of his routines: “What do you get if you divide the circumference of a jack-o’-lantern by its diameter? Pumpkin pi!” And the best part is, telling pi-themed jokes makes you sound smart while you’re making people laugh. Who says math can’t be fun?! Check out some of our favorite jokes about pi, and math in general, to celebrate Pi Day.

## Pi can go the distance

You can see what pi to one million decimal places looks like, here, at piday.org (keep scrolling!). Another way to visualize this super-long number? If you printed out pi to a *billion* decimal values, in 12-point font, you’d need a piece of paper that stretched halfway across the United States, from Kansas to New York City.

## Celebrate Pi Day with a 5K

Besides being a nice rhyme, a 5K is pretty close to 3.14 miles in length (it’s 3.10686 miles, to be exact). So schools and communities around the country host 3.14 mile runs on or near Pi Day every year. We found them in Newark, Delaware; Monroe, Connecticut; South Bend, Indiana; Green Bay, Wisconsin; and Tempe, Arizona. Find out which math lessons you’ll actually use in real life.

## Better yet, celebrate pi with pie

It’s already a Pi Day tradition: pie in all its glory! Pizza pie, pot pie, shepherd’s pie, and of course, dessert pie. Just make sure it’s round! Prefer a no-bake pie? Skip the oven with these 30 no-bake pie recipes you’ll want to make tonight.

## Pi’s double has some fans, too

It would seem that every massively popular thing inevitably has some detractors, too, and pi is no exception. A growing number of math lovers have begun to argue that a number called “tau,” which is two times pi, deserves at least as prominent a place in the math world as pi. Tau, whose approximate value is 6.28, is the relationship between the circumference of a circle and its radius, while pi relates the circumference to the diameter. Since the radius is a more useful mathematical quantity, many believe that tau is a more intuitive mathematic value than pi.

## Pi inspires poetry

You can also observe Pi Day with a poem… or a “piem”! Pilish unites math enthusiasts and word nerds. To compose in it, you must use words in which the number of letters corresponds, in order, to the numbers in pi’s sequence. So since pi = 3.14159, your poem must start with a three-letter word, then a 1-letter word, then a 4-letter word, another single letter, and so on: “Aha, I said, a fancy alligator …” Now, check out our 12 trickiest math riddles.