Pi Day

Updated August 5, 2020 | Infoplease Staff

A day to celebrate all things round

by Catherine McNiff

3.1415926535897932. . .

Approximated as 3.14, the Greek letter for pi is an irrational (cannot be written as a simple fraction), an infinite (continues forever), a non-repeating, a transcendental (incapable of being the root of an algebraic equation with rational coefficients) number. Pretty impressive for the 16th letter of the Greek alphabet.

Here's the breakdown:
Pi is the ratio of the circumference of a circle to its diameter. The diameter of a circle is the distance from one side of a circle to the other side, as measured by a straight line that passes through the center point. The circumference of a circle is the distance around (perimeter). With pi, you can find the circumference and area of a circle, and the volume and surface area of a sphere, cone, and cylinder. So why is pi so important? Pi stays the same—it is a constant—no matter the size of the circle. You could say that with pi, you come full circle.

Pi's Beginnings (Pi, Unbaked)

Some cheerleaders of pi trace its beginnings to the Old Testament where, in 1 Kings 7:23, Solomon casts a large vessel of specific dimensions: 30 cubits high and 10 cubits across, arguably an early reference to the ratio that will later be known as pi. Sometime during the third century B.C., Archimedes (287-212 BC) used polygons to approximate the measurement of pi, accurate to two decimal places. Meanwhile, the Babylonians, Egyptians, and the Chinese all had their hands in the pi. . .but it wasn't until the 18th century that pi was written as we know it today: a designation attributed to William Jones in 1706 and popularized by Leonhard Euler beginning in 1737.

Honorable Pi (No More Humble Pi)

In the 111th Congress, in House Resolution 224, humble pi became just a little more honorable (excerpt):

March 12, 2009.

Whereas the Greek letter (Pi) is the symbol for the ratio of the circumference of a circle to its diameter;

Whereas the ratio Pi is an irrational number, which will continue infinitely without repeating, and has been calculated to over one trillion digits;

Whereas Pi is a recurring constant that has been studied throughout history and is central in mathematics as well as science and engineering;

Whereas America needs to reinforce mathematics and science education for all students in order to better prepare our children for the future and in order to compete in a 21st Century economy;

Whereas Pi can be approximated as 3.14, and thus March 14, 2009, is an appropriate day for "National Pi Day": Now, therefore, be it Resolved, That the House of Representatives--

(1) supports the designation of a "Pi Day" and its celebration around the world;

(2) recognizes the continuing importance of National Science Foundation's math and science education programs; and

(3) encourages schools and educators to observe the day with appropriate activities that teach students about Pi and engage them about the study of mathematics.

This marked official acknowledgment of a day that had been celebrated since at least 1988, when an employee of San Francisco's Exploratorium, Larry Shaw, first started the Pi Day tradition. Now Pi Day is celebrated all over the world on March 14 (3/14).

Pi Bonanza

The year 2015 was extra special. An observation by M. Ratna Prabhu in India, who posted on piday.org, illustrates just what the "Pi Bonanza Year" 2015 represented:

  • In the mm-dd-yy format March 14, 2015 is written as 3-14-15. These are the first 5 significant digits of Pi (3.1415).
  • On this day, at 9 AM, it was the first 6 digits of pi. So this was the Pi Hour. (3.14159)
  • Twenty six minutes later, it was the Pi Minute (3.1415926).
  • Add 53 seconds and voila, the Pi Second. (3.141592653).
  • Now comes the most dramatic. . .by expressing the fractional part of the Pi Second in the form of decimals, say, 5.35 we get up to 11 digits of Pi. Then extending the decimals infinitely, as per the digits of Pi, we pass through the Perfect Pi Moment!!!

Interesting Pi Facts (Bits and Bytes about Pi)

  • Albert Einstein was born on 3-14 in 1879.
  • If you hold a mirror up to Pi (314), it spells PIE. Try it.
  • In October 2011, a 56-year-old Japanese systems engineer, Shigeru Kondo, successfully calculated the value of pi to 10 trillion digits. It took him a year on a homemade computer with a 48-terabyte hard drive. And, according to The Telegraph, the adventure of calculating pi as a hobby was not without its drama: Mr. Kondo's wife, Yukiko observed the practical issues involved in running a powerful computer—which produces significant heat—day in and day out: "We could dry the laundry immediately but we had to pay 30,000 yen ($390) a month for electricity."
  • Massachusetts Institute of Technology announces its regular action admissions decisions on March 14 at 6:28 PM, or, as they call it: Pi Day, Tau Time with a nod to the rival theory of tau as the better concept for calculations using pi. For the record, tau is 2pi.

Ways to Celebrate Pi Day (Have Your Piece of the Pi)

  • Make and eat a pie.
  • Throw a pie.
  • Visit Princeton, New Jersey where they celebrate Pi Day and Einstein's birthday. Einstein lived in Princeton while working at the Institute for Advanced Study. Be sure not to miss the Einstein look-alike contest.
  • Discuss the significance of pi with your friends.
  • See who can recite pi to the highest number of digits.
  • Read The Life of Pi.
  • Visit http://www.piday.org/ — it has a countdown to pi day!
  • Go to http://www.123greetings.com/events/pi_day/ to find free greeting cards to wish all those you love happy pi day
  • Check out MathMovesU.com to find a Pi Day for parents, students and teachers.
  • Visit the Exploratorium in San Francisco—or visit their website
  • Celebrate all things round!

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