# All things pi: How to celebrate one of the nerdiest holidays of the year

According to the "Guinness Book of World Records," Chao Lu from China was able to recite pi from memory to 67,890 places on Nov. 20, 2005. The feat took more than 24 hours to complete, and Lu said he studied the sequence for four years before his world record attempt.

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"in 2009 the United States House of Representatives passed a resolution that officially recognized the day."

I can think of roughly 3.14 reasons why this does well to illustrate how poorly our tax dollars are being used.

Pi is an irrational number, which means you literally can't write out all the digits. But if you're going to approximate pi, the accepted method is to pick a degree of precision (say, three decimal points) and write the digits up to that point, rounding the last one if necessary. Thus, pi to three decimal points is 3.142; pi to five decimal points is 3.14159; and so on. Contrary to the illustration that accompanies item #7 in this list, 3.145 is not a particularly good approximation of pi.

Let's start by acknowledging the importance of science, and knowledge in general.

Haha! Good catch. 3.145.

Question: How is pi considered a mathematical constant even though there is no final decimal number? For instance how c is a universal physical constant, but c ends in .0000etc, and pi never ends on the right of the decimal.

@SillyRabbit

In math, a constant does not have to be a rational number. A mathematical constant can be any number of special physical significance. In the case of pi, take the circumference of a circle and divide it by the diameter of that same circle and you get pi. What's cool is you get the same answer when you do the same thing to ANY circle of ANY size. That's why pi is a constant - because the value is the same no matter what circle you're trying this on.

Other irrational constants are Euler's number (e), Pythagoras' number (square root of 2), and the gravitational constant (G).

@Silly Rabbit

Pi is the equivalent of the fraction 22/7. While it is irrational and unending when the fraction is converted into decimal form, the number like seemingly all other numbers can be put into different or simpler forms that can be applied to various equations. If the fractional form is easier for you, then use it.

It is actually 3.1415..., not 3.145 as shown in one of the images.

Next year will be the big year, a once-in-a-lifetime event, on March 14, 2015, or 3/14/15 for 3.1415!

Thanks to you both for answering. It seemed contrary in my mind.

Irrationality is a concept that makes sense for purely mathematical constants such as e, pi, or sqrt(2), but it does not make sense for physical constants (e.g gravitational constant). Mathematical constants are computed theoretically and thus can be approximated with infinite precision. Physical constants are measured by an experiment and thus the precision is limited. E.g we cannot yet measure mass with the precision of 10^-100 kg, and if I am not sure if we ever could because things stop behaving quite the way we would expect them to when we get to a sub-atomic level and beyond - so the concept of mass in the traditional sense for a such a small object may after all be non-existent.