What's Pi Day All About? Math, Science, Pies and More

Math enthusiasts around the world, from college kids to rocket scientists, celebrate Pi Day on Thursday, which is March 14 or 3/14 — the first three digits of an infinite number with many practical uses.
Around the world many people will mark the day with a slice of pie — sweet, savory or even pizza.
Simply put, Pi is a mathematical constant that expresses the ratio of a circle's circumference to its diameter. It is part of many formulas used in physics, astronomy, engineering and other fields, dating back thousands of years to ancient Egypt, Babylon and China.
Pi Day itself dates to 1988, when physicist Larry Shaw began celebrations at the Exploratorium science museum in San Francisco. The holiday didn’t really gain national recognition though until two decades later. In 2009, US Congress designated every March 14 to be the big day — to hopefully spur more interest in math and science. Fittingly enough, the day is also Albert Einstein's birthday.
Here's a little more about the holiday's origin and how it's celebrated today.
WHAT IS PI? Pi can calculate the circumference of a circle by measuring the diameter — the distance straight across the circle's middle — and multiplying that by the 3.14-plus number.
It is considered a constant number and it is also infinite, meaning it is mathematically irrational. Long before computers, historic scientists such as Isaac Newton spent many hours calculating decimal places by hand. Today, using sophisticated computers, researchers have come up with trillions of digits for pi, but there is no end.
WHY IS IT CALLED PI? It wasn't given its name until 1706, when Welsh mathematician William Jones began using the Greek symbol for the number.
Why that letter? It's the first Greek letter in the words “periphery” and “perimeter,” and pi is the ratio of a circle's periphery — or circumference — to its diameter.
WHAT ARE SOME PRACTICAL USES? The number is key to accurately pointing an antenna toward a satellite. It helps figure out everything from the size of a massive cylinder needed in refinery equipment to the size of paper rolls used in printers.
Pi is also useful in determining the necessary scale of a tank that serves heating and air conditioning systems in buildings of various sizes.
NASA uses pi on a daily basis. It's key to calculating orbits, the positions of planets and other celestial bodies, elements of rocket propulsion, spacecraft communication and even the correct deployment of parachutes when a vehicle splashes down on Earth or lands on Mars.
Using just nine digits of pi, scientists say it can calculate the Earth's circumference so accurately it only errs by about a quarter of an inch (0.6 centimeters) for every 25,000 miles (about 40,000 kilometers).
IT'S NOT JUST MATH, THOUGH Every year the San Francisco museum that coined the holiday organizes events, including a parade around a circular plaque, called the Pi Shrine, 3.14 times — and then, of course, festivities with lots of pie.
Around the country, many events now take place on college campuses. For example, Nova Southeastern University in Florida will hold a series of activities, including a game called “Mental Math Bingo” and event with free pizza (pies) — and for dessert, the requisite pie.
“Every year Pi Day provides us with a way to celebrate math, have some fun and recognize how important math is in all our lives,” said Jason Gershman, chair of NSU's math department.
At Michele's Pies in Norwalk, Connecticut, manager Stephen Jarrett said it's one of their biggest days of the year.
"We have hundreds of pies going out for orders (Thursday) to companies, schools and just individuals," Jarrett said in an interview. “Pi Day is such a fun, silly holiday because it’s a mathematical number that people love to turn into something fun and something delicious. So people celebrate Pi Day with sweet pies, savory pies, and it’s just an excuse for a little treat.”
NASA has its annual “Pi Day Challenge” online, offering people plenty of games and puzzles, some of them directly from the space agency's own playbook such as calculating the orbit of an asteroid or the distance a moon rover would need to travel each day to survey a certain lunar area.
WHAT ABOUT EINSTEIN? Possibly the world's best-known scientist, Einstein was born on March 14, 1879, in Germany. The infinite number of Pi was used in many of his breakthrough theories and now Pi Day gives the world another reason to celebrate his achievements.
In a bit of math symmetry, famed physicist Stephen Hawking died on March 14, 2018, at age 76. Still, Pi is not a perfect number. He once had this to say:
“One of the basic rules of the universe is that nothing is perfect. Perfection simply doesn’t exist. Without imperfection, neither you nor I would exist.”

At a studio in central China's Hunan province, a teacher grips an ink brush, gently writing characters of a secret script created by women centuries ago and now being embraced by a new generation.

Nushu, meaning "women's script", emerged around 400 years ago. Barred from attending school, the women secretly learned Chinese characters and adapted them into Nushu, using the script to communicate with each other through letters, song and embroidery.

Passed down through generations of women in the remote and idyllic county of Jiangyong, it is now gaining popularity nationwide among Chinese women who view it as a symbol of strength.

Student Pan Shengwen said Nushu offered a safe way for women to communicate with each other.

"It essentially creates a sanctuary for us," the 21-year-old told AFP.

"We can express our thoughts, confide in our sisters and talk about anything."

Compared to Chinese characters, Nushu words are less boxy, more slender and shaped like willow leaves.

"When writing... your breathing must be calm, and only then can your brush be steady," Pan said.

Student He Jingying told AFP she had been enrolled in a Nushu class by her mother and that writing it brought her "a deep sense of calm".

"It feels like when the brush touches the paper, a kind of strength flows into you."

Against 'injustice'

Nushu is more than just a writing system -- it represents the lived experiences of rural women from the county, Zhao Liming, a professor at Beijing's Tsinghua University, told AFP.

"It was a society dominated by men," said Zhao, who has been studying Nushu for four decades.

"Their works cried out against this injustice," she said.

The words are read in the local dialect, making it challenging for native Chinese speakers not from the region to learn it.

Teacher He Yuejuan said the writing is drawing more attention because of its elegance and rarity.

"It seems to be quite highly regarded, especially among many students in the arts," He told AFP outside her gallery, which sells colorful merchandise, including earrings and shawls with Nushu prints.

As a Jiangyong native, He said Nushu was "part of everyday life" growing up.

After passing strict exams, she became one of 12 government-designated "inheritors" of Nushu and is now qualified to teach it.

'Really special'

An hour's drive away, around a hundred Nushu learners packed into a hotel room to attend a week-long workshop organized by local authorities trying to promote the script.

Zou Kexin, one of the many participants, told AFP she had read about Nushu online and wanted to "experience it in person".

"It's a unique writing system belonging to women, which makes it really special," said Zou, 22, who attends a university in southwestern Sichuan province.

Animation student Tao Yuxi, 23, one of the handful of men attending the workshop, told AFP he was learning Nushu to gain inspiration for his creative work.

He said his aunt was initially confused about why he was learning Nushu, as it is not typically associated with men.

As it represents part of China's cultural heritage, Nushu has to be passed down, he said.

"It's something that everyone should work to preserve -- regardless of whether they are women or men."

What's Pi Day All About? Math, Science, Pies and More