Today’s contribution is from friend of the site, Festival of the Spoken Nerd’s Matt Parker, who’s found a way to **approximate π using a mince pie** (or any type of pie, or indeed any small object with non-zero mass, but the mince pie is the most festive option). The trick is to use it as the weight on the end of a 2.45m-long pendulum, and time the swings.

The pendulum is part of the latest Spoken Nerd show, You Can’t Polish a Nerd (which we’ve reviewed here recently), and this clip shows Matt’s preparations to do the approximation live on stage:

#Maths doesn't get much more dramatic than this! Adventures in π-measurement with @standupmaths, from our latest show You Can't Polish A Nerd, available in a dazzling array of formats including 💾!

Head to https://t.co/OtdOSx4YEG to get yours! pic.twitter.com/Z3sSiwday8

— Spoken Nerd (@FOTSN) November 13, 2018

The diagram below outlines how it’s done:

- The period of a pendulum is a complete swing back & forth.
- Period time = $2\pi \sqrt{\frac{\textrm{length}}{g}}$
- Acceleration due to gravity on the Earth’s surface is about: $g = 9.8m/s^2$
- If the length of a pendulum is $\frac{9.8}{4} = 2.45m$ the period will be $\pi$ seconds.
- PRO TIP: For greater accuracy: leave your pi-endulum swinging for a while and divide the total time by the number of swings to get $\pi$.

Share your own photos, videos and approximations to mince π on Twitter, and give @FOTSN a mention so they can see just what they’ve started. Visit the FOTSN shop to get your hands on the show in various formats (great Christmas presents!).

*This post is part of the Aperiodical’s 2018 Aperiodvent Calendar.*