Monday 11 March 2013

Calculating Pi with Pies

Pi Day is celebrated on March 14 (3/14 - get it?)

It's a day of much interest for my Numberphile project.

Last year we posted four videos - see them here!

This year I decided on something more ambitious.

It turns out a friend of mine works for local pie company, Pukka Pies, so I pitched him an idea.

Calculate Pi using real pies.

In true "corporate style", I even made a small Powerpoint presentation to make the case, which included this stunning representation!

Sure enough the people at Pukka came through with about 400 pies.

The original plan was to make the video on a football pitch, utilising a centre cirle.

The people at Notts County FC (nickname, the Magpies or Pies!) agreed to let us use their pitch if we were careful (and thanks to the guys at the Copa90 football channel for making some introductions).

So we made the film at the stadium, but decided placing pies on the pitch might not be a good idea for several reasons.

1. The pitch is muddy and we would be on our knees a lot!

2. The centre circle was a bit too big - our pie circle would be smaller.

3. Being in the middle of a huge pitch might diminish or otherwise impressive circle - make it look smaller than it really was.

4. Being on a football pitch - a srange environment - might distract viewers from the purpose of  the video.


So after filming some explanatory segments on the pitch, we retreated to a nearby car park.

In front of the camera was "standup mathematician" Matt Parker - who traveled some distance for the shoot.

He's a man passionate about Pi and has had a few "pideas" himself over the years - when he heard I had hundreds of pies, he jumped at the opportunity.

(Matt was unwell on the day and was a trooper for seeing it through)

With me filming - assisted by a second cameraman James Hennessy for extra shots - Matt had sole responsibility for laying out the pies.

First he marked a circumference and diameter (using chalk and string) then laid out the circumference.

It measured 264 and 2/3 pies.

Then the diameter, which was 84 and 1/3 pies across.

Divide the former by the latter and our calculation for Pi was in the order of 3.13834

Real Pi starts with the figures 3.14159

So if you were rounding, both figures are 3.14

Pretty accurate - and we did not cheat or massage the figures in any way.  It was a totally honest experiment.


A short video (3:14 in duration, of course) has been uploaded today.

A longer version including the football pitch section will be uploaded on Pi Day itself.

PS: I believe it was a "noble death" for these pies to be used in such an educational way. However Numberphile has also donated £314 to a local charity which helps feed people at times of crisis.

1 comment:

  1. The pictures would've been a bit more original if you had done some aerial photography, though. Still a pretty cool video, I liked the idea a lot!