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What is Pi? And where did pie come from? And who mashed them together for Pi Day?

Facts about pi on Pi Day

March 14th is Pi Day. Here are some facts about the famous number.
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March 14th is Pi Day. Here are some facts about the famous number.

For certain people, March 14th each year marks Pi Day, the date 3.14 is the first three digits in the infinitely continuing number. It’s also Albert Einstein’s birthday.

“Pi Day is an annual opportunity for math enthusiasts to recite the infinite digits of Pi, talk to their friends about math, and to eat Pie,” according to PiDay.org. There’s also pizza involved.

Pi, the infinite number

Pi is “an irrational and transcendental number, it will continue infinitely without repetition or pattern,” PiDay.org says. It’s been calculated out to a trillion digits, the site states.

It starts: 3.14159, and that’s about all you need.

Pi is represented by a Greek symbol and is the “ratio of the circumference of a circle to the diameter,” according to math.com and math textbooks everywhere.

The concept of Pi goes back thousands of years, perhaps longer than pie or pizza, according to PC World’s 2013 “A brief history of Pi.”

“The Great Pyramid at Giza, which was built between 2550 and 2500 BC, has a perimeter of 1760 cubits and a height of 280 cubits, which gives it a ratio of 1760/280, or approximately 2 times pi,” PC World reports.

Written evidence of Pi dates back to 1900 BC, and PC World writes, it appears both the Babylonians and the Egyptians had a close approximation of the number.

Archimedes got close to calculating a precise number for pi, as did Zhu Chongzhi, a Chinese mathematician about 600 years later, PC World reports. And then there’s this passage from the Bible: “And he made a molten sea, ten cubits from the one brim to the other: it was round all about, and his height was five cubits: and a line of thirty cubits did compass it round about.”

In more recent history, Math.com states: “In 1761 Lambert proved that Pi was irrational, that is, that it can’t be written as a ratio of integer numbers. In 1882 Lindeman proved that Pi was transcendental, that is, that Pi is not the root of any algebraic equation with rational coefficients.”

But all this math history can make people hungry.

Pie, the baked good and the pizza variety

Pie, as it happens, also dates back to the ancient Egyptians. According to the History of Pies from the American Pie Council: “The first pies were made by early Romans who may have learned about it through the Greeks. These pies were sometimes made in ‘reeds’ which were used for the sole purpose of holding the filling and not for eating with the filling.”

“The first pie recipe was published by the Romans and was for a rye-crusted goat cheese and honey pie,” the American Pie Council writes, which sounds pretty good.

Meat pies became popular in England starting in the 12th century, according to the Pie Council, and the British credit Queen Elizabeth I with the first cherry pie.

Pizza pie is the youngest out of the Pi Day trio. “It was in late 18th-century Naples that the pizza as we now know it came into being,” according to History Today.

Naples saw a population boom as trade grew and peasants moved to the city from the countryside in the first half of the 1700s, History Today states, and that took a toll on the economy. Many workers lived in poverty and ate as they could. “Sold not in shops, but by street vendors carrying huge boxes under their arms, they would be cut to meet the customer’s budget or appetite,” History Today writes.

“As Alexandre Dumas noted in Le Corricolo (1843), a two liard slice would make a good breakfast, while two sous would buy a pizza large enough for a whole family,” according to the site.

The History Channel says fortunes changed for pizza with the unification of Italy. “King Umberto I and Queen Margherita visited Naples in 1889. Legend has it that the traveling pair became bored with their steady diet of French haute cuisine and asked for an assortment of pizzas from the city’s Pizzeria Brandi, the successor to Da Pietro pizzeria, founded in 1760.”

Pizza spread with the Italian diaspora, but didn’t start gaining real popularity in the United States until World War II, the History Channel reports.

But Pi Day?

Physicist Larry Shaw founded Pi Day in 1988, according to the History Channel. The first Pi Day celebration was at the Exploratorium, the San Francisco science museum, with a “circular parade and the eating of fruit pies,” the History Channel writes.

Congress made Pi Day official in 2009, according to CNET.

“In 2015, Pi Day fanatics had a special treat. Celebrations took place on 3/14/15 at 9:26:53 a.m., the numerical date and time together representing the first 10 digits of pi, 3.141592653,” according to the History Channel.

Now, March 14 is a day for pie baking contests, pizza specials and quality math jokes.

Why don’t you go up and talk to Pi at a party? Because it goes on forever.

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