Category Archives: Pi

The Great pi / e Debate

I had a very busy March, so I wasn’t able to do much for Pi Day this year. But, I am going to get in one more post before the end of Pi Month. That’s right, since this year is 2014, March 2014 (3/14) is Pi Month!

Here is a video from The Mathematical Association of America. It is “The Great pi/e Debate”, presented at Williams College during their First Year Family Weekend, in which two professors debate the relative merits of the numbers pi and e. Which is better? Watch the videos and decide for yourself.  Part 1 is mostly introductions, so if you prefer, just start in with part 2.

Happy Tau Day

As a math lover, I love that I share my birthday with τ (tau) Day. What is τ you ask? It’s 2π of course (τ = 2 x 3.14 = 6.28). Why give 2π a name and a day? Well, watch these 2 videos, one from Vi Hart and the other from Numberphile, to see what the fuss is all about.

Pi Video Round-up

I’ve been looking for some good videos to show the kids in our after-school math club. (We are lucky that we meet on Pi Day this year.) So, I thought I would post what I had found.

This short video explains that pi = circumference/diameter:

Another brief video. This one tells about some of the places, outside of circles, that we find pi:

This one is a bit longer. The first 10 minutes give a good history of pi, but the last 5 minutes devolves into a series of bad song and TV show clips:

This video (with a very old-school feel) has some nice animations illustrating the value of pi:

All of Vi Hart’s math videos are great.  Here are 2 of them involving pi:

Here is the video by Numberphile, explaining that you only need 39 digits of pi:

And, of course, the pi song:

39 Digits of Pi


The more digits of pi you use, the more accurate your calculation. For example, using 3.14 is more accurate than using a value of 3. The value of pi has been calculated to trillions of digits (the record at the time of this post is a little over 10 trillion digits). However, the push for more and more digits of pi has more to do with a desire to break records and test computer algorithms than any need to be more accurate. It would never be necessary to use more than a few digits of pi. In fact, you only need 39 digits of pi to calculate the circumference of the known universe to an accuracy that is within the width of a single hydrogen atom.

Pi rounded to 39 digits: 3.14159265358979323846264338327950288420

Numberphile explains the calculation in his video:

Pop Culture Pi

  • In the Star Trek episode, “Wolf in the Fold,” the ships computer is taken over by an evil entity named Redjac. Spock thwarts Redjac, by commanding the computer to “compute to last digit the value of pi”.
  • In Carl Sagan’s novel Contact, scientists compute pi to a record number of decimal places and find a pattern in its digits believed to be a message from the creators of the human race.
  • During the O.J. Simpson trial, FBI agent, Robert Martz, misstated the value of pi, undermining his value as a witness.
  • In Darren Aronofsky’s 1998 psychological thriller Pi, the main character is driven mad by his attempt to find a number that will unlock the patterns in nature.
  • In an episode of The Simpsons, Professor Frink gets the attention of a group of scientists by shouting Pi is exactly 3!”.

How many digits of Pi do you know?

Most people know 3.14; a few know 3.14159. But, some people take it much further. The record for reciting the most digits of pi is currently held by Lu Chao from China. In 2005, he recited 67,890 digits of pi. The recitation took 24 hours and 4 minutes. He said that after 1 year of memorization, he had memorized 100,000 digits. He had planned to recite 91,300, but he made a mistake with the 67,891st digit, saying “5” instead of “0”.