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Pi Day

This Friday is Pi Day. March 14, or 3/14… 3.14… π… get it?

πPi day is celebrated in many places around the world every year on March 14th. The physicist Larry Shawn organized the first official, large-scale celebration in 1988 at the San Francisco Exploratorium, an American museum. In 2009, the United States passed a non-binding resolution to recognize March 14th as the National Pi Day.

The day is celebrated in honor of the constant π (pronounced pie), and is spent eating or throwing pies. It is observed in many schools, and some of them hold competitions to determine which student can remember the highest number of decimals.

The MIT, a university in Massachusetts, is known to have sent application decision letters to prospective students for delivery on Pi Day. Since 2012 though, they post those decisions online on that day.

What’s all the fuss about?

π is a mathematical constant which represents the ratio of a circle’s circumference to its diameter, a value that approximately equals 3.1416. In order words, if a circle’s diameter is measured at 1 cm, than its circumference is about 3.14 cm.

This is very useful in many fields where geometry is used. It is used in architecture where a circle is to be built, since it is more convenient to build it by measuring a diameter, but you will need to know the circumference in order to measure the surface. For instance, you will build a round swimming pool around its diameter, but you need to know how much cement will be needed to fill the bottom. In engineering, it is used to build engines for instance, as they generally have a lot of round parts. π is used in statistical distributions, including many random number generators. You will need π to calculate how much soil is needed to fill that pretty circular patch of flowers. Now imagine the face on the salesperson when asking for 18.45 kg of soil, because you don’t want to pay for more than needed.

Pi-eq-C-over-dπ is part of your life. Your planet is round, isn’t it? So it can be measured with π. Maps of large areas are drawn using π in order to keep a precise projection.

π is an irrational number, meaning that the decimals never end and they don’t form any repeating pattern. It cannot be expressed as an exact fraction.

Since it is impossible to represent the exact value of π, an approximation is always used, with a precision based on the purpose. For everyday use, you won’t need much precision, but astronomers may need several hundred decimal digits of precision or miss their target by several kilometers.

A common approximation in use today is 22/7 (3 + 1/7), which is about 3.1429. Correct to only two decimal places, the error may be considered insignificant for many purposes.

In 2006, the Japenese engineer Akira Haraguchi set the current world record for reciting 100,000 digits of π in 16 hours. However, the Guinness Word Records did not approve the effort and currently recognizes the Chinese Lu Chao who recited π to 67,890 decimal digits without error in 24 hours and 4 minutes in 2005.

In 2010, Shigeru Kondo and Alexander Yee broke the record for the most digits of π ever calculated. With a software designed by Yee and a computer assembled by Kondo, it took 90 days to calculate five trillion digits. The result was saved on a cluster of 20 external hard drive, culminating to 32 terabytes of data.

According to astronomer Simon Newcomb:

Ten decimal places of π are sufficient to give the circumference of the Earth to a fraction of an inch, and thirty decimal places would give the circumference of the visible universe to a quantity imperceptible to the most powerful microscope.

But if you feel the need, here are 100,000 digits of π.

When did it all started?

The earliest known references to π are from a Babylonian clay tablet dated 1900-1600 BC which states a value of 25/8 (3.1250), and an Egyptian papyrus dated 1650 BC where the value is stated as (16/9)2 (3.1605). Let’s note that both approximations are within 1% of error. Neither cultures had any symbol to represent the value though.

The Great Pyramid of Giza, which construction was completed by the Ancient Egyptians around 2566 BC, has a ratio of height to perimeter of about 6.2857, a value that is one tenth of 1% of error from 2π. Some Egyptologists concluded that the pyramid must have been built using π, but others maintain that the anecdote is a mere coincidence since no evidence exists of the knowledge of the value at such an early date. Despite any evidence, it wouldn’t surprise me since the Great Pyramid was built with an extreme precision that many modern architects cannot achieve. On the other hand though, the implication of π is so great in general geometry that it might just have been a logical outcome.

The symbol π, a Greek letter corresponding to the Latin letter p (and which should correctly be pronounced as pee despite being usually pronounced as pie by English speakers), was first used by the Welsh mathematician William Jones in 1706. Jones states that he borrowed his knowledge from the astronomy professor John Machin, who is known for a method of calculating π to a precision of 100 decimals, so it is possible that Machin actually used the Greek letter in this context first. It is to note that the English mathematician William Oughtred used the π symbol in the context of geometry as early as 1647, but not exactly for the concept commonly attributed to π today.

What will you do?

What will you be doing for Pi Day? Will you eat pies? Will you discuss the implications of π in your daily life? Will you set up a round patch of flowers? Will it be just another day? Come on, don’t be square! Let me know in the comments below.

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5 comments on “Pi Day

  1. sledpress
    March 13, 2014

    As long as we have cats, who sleep circular, we are covered for Pi Day observance, I think.

    I was bashed so much in school for being a dub at math (“you’re smart so the only reason you didn’t do better on this test is that you’re lazy and goofing off! Detention for you!”) that there are days I never want to see a number again… I wish it were different so that I could enjoy this sort of thing.

    • Tom Duhamel
      March 13, 2014

      I get you. I was always good at math, but I hated how it was taught. If I had knew what each bit was good for, I would have learned and memorized every bit. But I could not figure what these things were good for, so I would learn just enough for exams and then forget everything.

      As an adult, I can’t enumerate just how many times I stumbled on a programing task and wished I had listened in class. There are just so many apparently simple tasks when writing a program which require particular math formulas/concepts… I had to relearn a lot of these things as an adult, and I never forget them again because now I knew what it was good for.

      As for the post, I wasn’t exactly serious. I just thought it was a light and fun subject to cover. Everyone knows the basic concept of Pi, but little is known about the history part of it. I like history, so I just wanted to explore that a bit and have a little fun on the way.

      • sledpress
        March 14, 2014

        I understand my Cute Engineer is baking a pie tonight and participating in a pie contest. It’s probably the peak of the year for an engineer who is also a terrific cook.

        But it does weird me out. I mean, the man ENJOYS making spread sheets and performing calculations. Which is good, since it’s how he earns his living, but from where I sit it seems perverted, like enjoying being waterboarded.

        I always thought that there should be high school classes in fully practical things like balancing a check book. As it was taught, it always seemed to me that
        math was one big game of “gotcha!” with the object of panicking you into arriving at the wrong answer or giving up so people could dump on you. I think it sort of sets the theme for filing tax returns in adult life.

  2. potsoc
    March 13, 2014

    I hate maths and for me π is really pie (or pee) in the sky even more so since it seems so usefull for astronomers. Just wish the engineers and architects busy on our future Champlain bridge know how to use it.

    • Tom Duhamel
      March 13, 2014

      If you were a millionaire, you’d love maths. But for the rest of us, all our maths seem to end up in a negative red number at the bottom of our bank account.

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This entry was posted on March 13, 2014 by in History and tagged , , , , , , .
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