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The mystery of Pi

Maths and the search for truth (Pi Approximation Day 22 July 2014)

by Paul Hess

Suitable for Whole School (Sec)


To show how all knowledge is partial and the search for truth is unending.

Preparation and materials

  • Have available one of the video clips below and the means to play it in Step 2 of the assembly to illustrate the concept of Pi (optional). The first two clips listed consist mainly of numbers and give a sense of the length of Pi, while the third is a Pi rap, after Eminem, which students might find entertaining. There are more musical versions of Pi on the Internet to enjoy!
    Alternatively, you may wish to write out some of the numbers of PI or ask your students to in order to give a visual sense of its length. 
  • In addition, you could play a clip from the film The Life of Pi to illustrate Step 5 (visit:


  1. Maths is often used to emphasize that we can be certain of something. For example, we use the phrase ‘as two plus two makes four’ to indicate something that we are absolutely sure of.

    Indeed, in philosophy, maths has also long been used as a basis for attaining knowledge that is certain and completely reliable. It was for this reason that Plato loved maths. He said, ‘geometry will draw the soul towards truth and create the spirit of philosophy’.

  2. Even though maths is used in this way, as an elegant and brilliant example of the attempts of human beings to understand the universe, it is itself incomplete. There are some things that even the greatest mathematicians cannot calculate precisely. Perhaps the best example of this is the number Pi.

    Watch the following video clip about Pi.

    Play chosen video clip, if using.

  3. Pi is the numerical value of the ratio of a circle's circumference to its diameter, approximately equal to 3.14. As the clip we have just watched makes clear, however, the decimal places after the ‘3’ never end and never settle into a permanent repeating pattern. For centuries, mathematicians have tried to pin down the number Pi and, so far, computers have calculated it to about 2.6 trillion decimal places! 

  4. I am sure I don’t need to tell you that 22 July is Pi Approximation Day! It is held on this day because 22/7 is the approximate value of Pi (which is equal to 3.14, which is why there is also another Pi Day on 14 March). It is a day on which to celebrate this mysterious number and the continuing efforts to calculate it precisely. No matter how hard we try, though, Pi seems to be stubbornly infinite!

  5. Many of you will have read and/or watched the film The Life of Pi. In the story, Pi is a young man who explores many different religions and goes on an incredible sea journey in order to find God. The Life of Pi seems to be saying that the search for truth is mystical and continually unfolding, like the number Pi itself.

    Play the video clip from The Life of Pi, if using.

  6. Of course, some people – whether they be mathematicians, scientists or religious believers – think we should be more definite and certain about truth. They believe that it is possible to find the absolute truth – and it is very important we do.

    The problem with the idea of being absolutely certain that you have found the truth, however, is, inevitably, it also makes you certain other people have not found it and they are wrong in what they believe. 

  7. A very well-known and wise Christian monk called Thomas Merton wrote very powerfully in Thoughts in Solitude about the Christian life not being about certainties, but, rather, about a search:

    My Lord God, I have no idea where I am going. I do not see the road ahead of me. I cannot know for certain where it will end  . . .  Therefore will I trust you always though I may seem to be lost and in the shadow of death. I will not fear, for you are ever with me, and you will never leave me to face my perils alone.  

    Like the search for the number Pi, therefore, the search for truth seems to be unending.


Time for reflection

In 1 Corinthians 13.12 (NRSV), Paul tells us that our knowledge of the divine is limited, incomplete and imperfect: 

For now we see in a mirror, dimly, but then we will see face to face. Now I know only in part; then I will know fully, even as I have been fully known. 

Paul seems to be warning us against the arrogance of certainty, yet encouraging us to continue the search for truth.  

You said, ‘Seek and you shall find’.
Save us from the arrogance of believing that we have all the answers,
but grant us inspiration, humility and wisdom in our own search for truth. 


Publication date: July 2014   (Vol.16 No.7)    Published by SPCK, London, UK.
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