Reid Champagne, The (Wilmington, Del.) News Journal

If mathematics is the language in which the universe and the Earth speak to us, thenthe diminutive constant pi would be an important component for that language.

"That's a very good way of looking at math and pi," said Tom Fernsler, of the Math Science Educational Resource Center at the University of Delaware. "Everything today that's made that is round or requires a calculation involving a circle, sphere or curved surface involves the use of pi."

It's even got its own "Day." March 14 is designated as Pi Day, as the calendar day representation of 3/14 matches the first three digits of pi (3.14).

**STORY:**Five ways to celebrate 3.14159 on Pi Day

That's just the tip of the geeky iceberg, but we'll circle back to that in a moment. It was Greek geek Archimedes who first correctly identified the ratio of a circle's circumference to its diameter as 22/7.

"Every circle regardless of size contains precisely that ratio," said Fernsler. "If there is any other ratio calculated other than 22/7 for the spherical entity you are measuring, then it's not a circle."

In other words, an oval or an ellipse does not have a ratio of 22/7, and may be considered circular, but are most definitely not circles. But 22/7 is but a crude representation of the precise measure of pi.

"Pi is an irrational number," Fernsler explained. "That means its decimal representation does not end, nor is it repeated."

For example, 1/2 is .5 decimally stated. 1/8 is .125. Both end and contain no repetition of decimal places. Such numbers are called "rational" numbers. The fraction 1/3, however, is .3333333, etc. Its decimal equivalent repeats and doesn't end. That makes it an "irrational" number. ("Rational" is a mathematical term and does not in any way suggest a rational number to be sane, or an irrational number to be insane.)

Pi is irrational, and that's where the fun begins, as long as fun for you includes memorizing and reciting pi out to thousands of decimal places. That turns out to be one of the many events that have been taking place in Princeton, N.J., each year on March 14.

"The idea came from doing something to commemorate Albert Einstein's birthdate of March 14," said Mimi Omiecinski, founder of Princeton's Pi Day, now in its fifth year. She was surprised how that inaugural event caught on. "We would have been happy with a handful of attendees," said Omiecinski. "But 1,500 people filled the library building on a day a Nor'easter was pounding the area."

This year's events over a six-day period, which are expected to draw a crowd of 6,000 plus, will include the pi recitation contest, along with an Einstein look-a-like contest, pie- (not pi) eating and judging contests and a walking tour of Einstein's neighborhood.

"It's a celebration during which a geek can feel like a rock star," said Omiecinski.

Professor Barry Renner, chair of the Department of Mathematics at Wilmington University, puts Pi Day into a larger, more significant context.

"Anything which popularizes math and helps to show it as something fun is a worthwhile activity."

**The skinny on pi**

**• World famous.**Pi is the most recognized mathematical constant in the world.

**• Around the Earth.**If the circumference of the Earth were calculated using pi rounded to only the ninth decimal place, an error of no more than one quarter of an inch in 25,000 miles would result.

**• Pi baby.**Albert Einstein was born on Pi Day (3/14/1879) in Ulm, Germany.

**• Are you a piphilologist?**Piphilology is the study and creation of mnemonic techniques for memorizing the never-ending string of decimal digits of pi. The technique of memorizing lines of poetry (known as a "piem") or prose is one of the best known. When the letters in each of the words in the phrase "How I want a drink, alcoholic of course, after the heavy lectures involving quantum mechanics" are counted, they correspond to the numerical 3.14159265358979 (carrying pi to 14 decimal places) and you become a hit at geek parties.

**• Is pi carried to one trillion digits overkill?**While modern computers are capable of calculating pi to one trillion decimal places, it doesn't do much practically for science. According to mathematicians Jörg Arndt and Christoph Haenel, 39 digits are sufficient to perform most calculations, because that is the accuracy necessary to calculate the volume of the known universe with a precision of one atom.

**• Pi cheers.**School spirit at the Massachusetts Institute of Technology has been memorialized in the cheer: "Cosine, secant, tangent, sine 3.14159."

**• You can't get there from here.**UD's Tom Fernsler says pi was essential to the calculations that landed a man on the moon. "Reaching the moon required the rendezvous of two separate spacecrafts," Fernsler said. "That meant the intersection of two spherical orbits required calculations involving pi." In other words, without Archimedes, there would be no Neil Armstrong.

**• Pyramid scheme.**Egyptologists have been fascinated for centuries by by evidence that suggests the Great Pyramid at Giza seems to approximate pi. The vertical height of the pyramid has the same relationship to the perimeter of its base as the radius of a circle has to its circumference.

**• Pi and the arts.**"The Little Constant That Could" has wound its way into artistic expression. Carl Sagan used the digits of pi to suggest a secret message from God in his novel "Contact." The 1998 movie "Pi" concerns a mathematician looking for a number to explain the meaning of existence. The Oscar-winning film "Life of Pi" actually has nothing to do with the constant's calculation or possible hidden meanings. (Though the movie does feature a cool CGI tiger that probably used pi in its design computer calculations.)

**• The granddaddy of all Pi Days?**San Francisco's Exploratorium is hosting its 25th annual Pi Day. Its website (www.exploratorium.edu/pi/index.html) states the annual celebration has grown into an international and online event. Included are pie-making and -throwing exhibitions.

**• Trekkie pi.**In the Star Trek episode "Wolf in the Fold," Spock foils the evil computer by commanding it to "compute to the last digit the value of pi."

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