Cómo funciona Pi

La definición de pi es simple: es la proporción de la circunferencia de un círculo dividida por su diámetro. Pero lo que es notable es que no importa el tamaño del círculo que esté midiendo, la relación entre la circunferencia y el diámetro siempre será igual a 3,1415926535897, normalmente abreviado a 3,14. Divida la circunferencia de una pelota de tenis por su diámetro y obtendrá 3,14. Divida la circunferencia del planeta Marte por su diámetro y obtendrá 3,14. Divida la circunferencia del universo conocido por su diámetro: obtendrá el punto. Como dijo un matemático , "Pi es parte de la naturaleza del círculo. Si la relación fuera diferente, no sería un círculo".

La siguiente figura muestra cómo la circunferencia de un círculo con un diámetro de 1,27 pulgadas (32,35 milímetros) es igual a una distancia lineal de 4 pulgadas (10,16 centímetros):

Como puede imaginar, 4.0 (la circunferencia) / 1.27 (el diámetro) = 3.14.

Pi is critical to several basic calculations in geometry, physics and engineering, including the area of a circle (πr2) and the volume of a cylinder (πr2)h. When the ancient Babylonians attempted to measure the precise areas of circles back in 1900 B.C.E., they assigned a value to pi of 3.125. The ancient Egyptians came up with 3.1605. The Greek mathematician Archimedes (287-212 B.C.E.) and the Chinese mathematician Zu Chongzhi (429-501 C.E.) are co-credited with calculating the most accurate approximations of pi before calculus and supercomputers gave us the definitive answer [source: Exploratorium].

In 1706, the self-taught Welsh mathematician William Jones assigned the Greek letter π to this magical number without end, possibly because π is the first letter of the Greek words for periphery and perimeter. The symbol's use was later popularized by 18th-century Swiss mathematician Leonhard Euler but wasn't adopted worldwide until 1934.

The fact that pi can be found everywhere — not only in circles, but in arcs, pendulums and interplanetary navigation — and that it's infinitely long has inspired a cult following that includes plenty of geeky tattoos and even its own national holiday. Keep reading to learn how you, too, can celebrate National Pi Day.

National Pi Day was officially recognized by the United States Congress in 2009, but the (definitely not "square") roots of the holiday can be traced back to 1988 and a man named Larry "The Prince of π" Shaw [source: Exploratorium]

Shaw was a beloved longtime employee at the Exploratorium, a science museum in San Francisco, California, and came up with the idea of "π Day" on a 1988 staff retreat following the death of Exploratorium founder Frank Oppenheimer. It was almost too perfect: The first digits of Pi are 3.14 — March 14!

Even better, March 14 is also Albert Einstein 's birthday, making π Day the ultimate geeky double-header.

The first π Day celebration was nothing more than Shaw and his wife handing out slices of fruit pie and tea at 1:59 PM (the three digits following 3.14), but the holiday quickly gained fame in the Bay Area.

Shaw eventually built the "Pi Shrine" at the Exploratorium, a circular classroom with a circular brass plaque at its center. Every Pi Day celebration at the Exploratorium ended with a colorful parade led by Shaw blasting his boombox (with a remix of "Pomp and Circumstance" set to the digits of pi) and circling the Pi Shrine exactly 3.14 times. The parade ended with the singing of "Happy Birthday" to Albert Einstein.

The Prince of π passed away in 2017, but the annual Exploratorium party continues, as do π Day celebrations the world over. Popular ways to celebrate include baking a pie and other circular treats; making a construction paper pi chain, where each 10 digits is a different color; and creating a collage out of circular shapes [source: National Pi Day].

You can also challenge your friends to a pi memorization contest. For a little context, the current world record for memorizing and reciting the most digits of pi was set by Suresh Kumar Sharma of India in 2015 when he recited a staggering 70,030 digits in 17 hours and 14 minutes. Why don't you start with 20?

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