Pi. Almost everybody’s favorite irrational number – irrational meaning that it cannot be accurately expressed as a fraction since it never (ever) comes out even, but continues, without repeating, past its decimal point and on into infinity. Pi has been computed to over one trillion decimal places (and counting).
In 2009 the U.S. House of Representatives formally recognized March 14 as National Pi Day.
It shares the date with Albert Einstein, who was born on it in 1879.
ALL ABOUT PI
In Cindy Neuschwander’s picture book Sir Cumference and the Dragon of Pi (Charlesbridge Publishing, 1999), Sir Cumference (in an attempt to alleviate a stomach ache) gulps down a potion that promptly turns him into a firebreathing dragon. His son Radius sets out to find a cure – which ultimately involves a magic circlerelated number (you’ll never guess what). One of the Math Adventure series, all starring Sir Cumference, his wife Lady Di Ameter, and son Radius, for ages 711.  
The Circle’s Measure is a mathbased lesson plan to accompany the book, with background information and activities.  
Johnny Ball’s Why Pi? (Dorling Kindersley Children’s Books, 2009) is a terrific 96page history of measurement from ancient times to the present. The book is beautifully designed, crammed with bright illustrations, clear diagrams, and a wealth of kicky facts and comparisons. Pi is in there, of course – but readers also discover how Egyptian built pyramids, how Romans built aqueducts, and how people figured out how to measure everything from the length of a month to the speed of light. Also included are puzzles and activities. For ages 7 and up.  
David Blatner’s The Joy of Pi (Walker & Company, 1999) is a fun 144page read for teenagers and adults, packed with illustrations, quotations, factoids, cartoons, and limericks. Included are a detailed history of pi, quirky anecdotes about the many people who have been obsessed with it – including the story of the Chudnovsky brothers, who calculated pi to two billion digits in their Manhattan apartment using a homemade supercomputer, and accounts of pi memory champions.  
For more on pi, see the Joy of Pi website.  
BrainPop’s Pi is a short animated movie for grade 3 and up (hosted by Tim, a human, and Moby, an orange robot) which defines pi, explains irrational numbers, and demonstrates the use of pi in calculating the circumference and area of a circle. Accompanying the movie are a handson activity (involving circles and string), a Q&A list, and a quiz.  
Also from BrainPop, see Circles.  
The BrainPop site has many similar short animations in the fields of math, science, social studies, English, arts and music, health, and engineering and technology. The drawback: it’s pricey. An annual subscription for a homeschooling family (24hour access, multiple users) costs $205. However, there’s a fiveday free trial option for those who would like a quick peek.  
For those within reach of San Francisco, the San Francisco Exploratorium hosts an annual Pi Day celebration, complete with pibased numerical parade. Visit the Exploratorium website for a brief history of pi, handson pi activities, and a list of helpful links.  
Teach Pi has suggestions for activities and projects, arts and crafts, songs, challenges, and contests for students of all ages.  
From the University of Arkanasa, the Amazing History of Pi is a history of calculations of pi beginning in ancient times (plus a list of fun pirelated stuff). For middleschool students and up.  
A History of Pi from the MacTutor History of Mathematics Archive traces the evolution of the number from the Egyptian Rhind Papyrus and the Bible to the present day. A more challenging mathematical approach for older kids.  
For the first one million digits of pi, see Pi to a Million Digits. 

The classic probability experiment known as Buffon’s Needle generates a statistical estimate of the value of pi. The idea for the experiment was first proposed in the 18^{th} century by Georges Louis Leclerc, Comte de Buffon who initially tried to measure pi by tossing loaves of French bread over his shoulder onto a tile floor.  
The proof of Buffon’s hypothesis requires calculus – but even precalculus kids can get the idea using this virtual needledropping simulation.  
For the full scoop, calculus and all, see Buffon’s Needle Problem at Wolfram MathWorld.  
From the National Council of Teachers of Mathematics, Celebrate Pi Day has articles, links, lesson plans, and activities for Pi Day, including a Buffon’s Needle demo using frozen hotdogs.  
One species of ant uses Buffon’s Needle to measure the sizes of potential nesting sites. Find out how at Ivars Peterson’s Buffon’s Needling Ants.  
Also see Peterson’s essay A Passion for Pi.  
Some people have a passion for memorizing pi. See the Pi World Ranking List for a list of champions (and instructions for how you too can get on it). (Warning: there’s stiff competition. The current champion is Chao Lu of China, who in 2005 rattled off pi to 67,890 digits.  
Your very own Pi Day! Find your birthday in pi here. 

Pi = 3?  Did Alabama – or maybe Indiana – ever actually enact legislation redefining pi as just plain 3.0? No, according to Alabama’s Slice of Pi. 
PI PROJECTS AND ACTIVITIES
Ed Emberley’s Picture Pie (LB Kids, 2006) is an art project book that shows kids – step by step – how to use papercut circles and fractions of circles to make animals, bugs, flowers, and patterns. For ages 4 and up.  
Pi Activities has suggestions for making a pi paper chain, measuring pi on a basketball court, and estimating pi using bicycle wheels and hula hoops.  
MathForum’s Making a Pi Necklace has instructions for making a pi bead necklace using storebought or handmade polymer beads.  
Art Projects for Kids and Kids Artists both have directions for gorgeous concentric circle projects based on the art of Kandinsky.  
The Concentric Circle Project is an art activity using paper cutout circles.  
PIKU  From a tenthgrade math teacher, PiKu Poetry has suggestions for pibased poetry – that is, “piku,” or haikus about pi – and pibased graphic art projects, with many examples of student work. 
The obvious accompaniment to Pi Day dinner: pie. See this recipe for making a pishaped Drunken Irish Apple Pi(e). 
MUSICAL PI
Pi Songs and Jokes has the lyrics to several pithemed songs, to be sung to such wellknown tunes as “Happy Birthday to You,” “O Christmas Tree” (O number pi/O number pi/Your digits are unending), and “Jingle Bells.”  
YouTube’s “The Pi Song” is a vocal rendition of pi to many many places. It’s a little monotonous, but surpisingly addictive.  
Steven Rochen’s violin piece, “A Piece of Pi” is a pibased violin piece by Steven Rochen. Listen to it here. Or try it: “A Piece of Pie” sheet music for violin or viola is available from Ovation Press. 
PI IS…WRONG?
Well, no. There are some mathematicians, however, who argue that the better and more fundamental constant is tau – which represents the relationship of circumference to radius (rather than diameter) and is thus twice as big as pi.
2 x pi = 6.28….which means that Tau Day is celebrated on 6/28. (Mark your calendars.)
Happy Pi Day: Let’s Kill It! explains – via a clever video from Vi Hart and a short text from Wired magazine – just why tau is the far better circle constant.  
The Tau Manifesto by physicist Michael Hartl is a spirited defense of tau, best appreciated by students with background in trigonometry.  
At What Tau Sounds Like, visitors can listen to a musical interpretation of tau by musician Michael Blake. 
ALBERT EINSTEIN: Born March 14, 1879
Dan Brown’s Odd Boy Out: Young Albert Einstein (Sandpiper, 2008) is a picturebook biography for ages 610, charmingly illustrated with penandink and watercolor. What readers take away from this one – I hope – is that, though those with different learning styles sometimes don’t fit in, they still can find their own way. Einstein has problems: his mother thinks his head is too big; his family calls him dopey; his teachers find him frustrating. At the same time, he’s forging an education of his own – he’s fascinated by a compass; he spends hours building a 14story house of cards; he teaches himself geometry with the help of a friendly medical student – and ultimately his oddness is spectacularly vindicated. For ages 48.  
Mike Venezia’s Albert Einstein: Universal Genius (Children’s Press, 2009) in the extensive “Getting to Know the World’s Greatest Scientists & Inventors series is an appealing 32page picturebook biography, illustrated with photographs and Venezia’s trademark humorous cartoons. A short catchy introduction to Einstein for ages 710.  
Kathleen Krull’s Albert Einstein (Viking Juvenile, 2009) in the Giants of Science series is an interesting and wonderfully written 128page account of Einstein’s life and work. The book is substantive and informative, but it’s Krull’s knack for human interest and lively phrasing that cause it to stand out from the oftendull biographical crowd. For ages 10 and up.  
Frieda Wishinky’s Albert Einstein (Dorling Kindersley Children’s Books, 2005) is an attractively presented 128page biography, illustrated with many modern and period photographs. For ages 10 and up.  
Einstein for Beginners by Joseph Schwartz and Michael McGuinness (Pantheon, 2003) is a multifaceted, catchy, and clever graphic presentation – yes, cartoons, but sophisticated cartoons – of Einstein’s life, times, and scientific accomplishments. A good pick for ages 12 and up.  
Gravity’s relationship to the curvature of spacetime is hardly a simple concept, but Bruce Bassett’s Introducing Relativity: A Graphic Guide (Totem Books, 2005) – an illustrated historical approach to Einstein’s famous theorem – is a good bet for interested teenagers.  
E = mc^{2}  By David Bodanis, E = mc^{2}: A Biography of the World’s Most Famous Equation (Berkley Books, 2000) is history and science for a popular audience. The book covers the components of the equation one by one (E, m, c, and squared), plus accounts of the many scientists whose research preceded Einstein. For teenagers and adults. 
E = mc^{2}  Why Does E=mc^{2}? by theoretical physicists Brian Cox and Jeffrey Forshaw (Da Capo Press, 2010) is a fascinating and readerfriendly approach to Einstein’s special theory of relativity and modern physicists’ views of the universe. For teenagers and adults. 
Einstein: His Life and Universe (Simon & Schuster, 2008) by Walter Isaacson – famed for his bestselling biographies of Benjamin Franklin and Steve Jobs – is a fascinating read for older teenagers and adults.  
This collection of Einstein’s WWIIera letters to Franklin Roosevelt begins with his letter of 1939, generally believed to have instigated America’s race to build an atomic bomb. Einstein later referred to this as the greatest mistake of his life.  
The PBS/NOVA program Einstein’s Big Idea is the story of E=mc^{2} – the “world’s most famous equation.” Included at the website are interactive activities, demonstrations, an Einsteinian timeline, a teacher’s guide, and a resource list.  
What became of Albert Einstein’s brain? Find out at Neuroscience for Kids.  
Michael Paterniti’s Driving Mr. Albert: A Trip Across America with Einstein’s Brain (Dial Press, 2001) is the story of an eccentric crosscountry road trip in which Paterniti and elderly pathologist Thomas Harvey set off to return Einstein’s brain to his granddaughter in California. A great read for teenagers and adults – and it provides, incidentally, a lot of information about Einstein.  
Inside Einstein’s Universe, a joint project of NASA and the HarvardSmithsonian Center for Astrophysics, has a collection of learning resources on Einsteinian cosmology including detailed downloadable teacher’s guides and interactive web resources for grades 712. 
2 Comments
thanks for sharing our concentric circles art project!
I got educated here — and will be celebrating Tau Day on June 28th. Meanwhile, don’t forget the best pi song (pi is only a small part of it, granted, but it beats the others hands down for musicality), “18 Wheels on a Big Rig” by Heywood Banks, performed by Trout Fishing in America and animated by Sean Sallings.