The first 200 people to sign up at https://brilliant.org/stevemould will get 20% off an annual subscription. Putting ballpoint pen ink on the tip of a leaf then putting it on water (or milk if you want it to stand out) causes the leave to whizz around leaving trail of ink behind. Here's the video I did with Matt using oleic acid to calculate pi: https://www.youtube.com/watch?v=lmgCgzjlWO4 Here's my spinning glue video: https://www.youtube.com/watch?v=38XWz1IL6j8 You can buy my books here: https://stevemould.com/books You can support me on Patreon here: https://www.patreon.com/stevemould just like these amazing people: Frank Hereford Will Ackerly Brendan Williams Matthew Cocke Frederic Merizen Joel Van der loo Glenn Watson Doug Peterson Paul Warelis John Zelinka Alnitak Grant Hay Heather Liu Marshall Fitzpatrik Lukas Biewalk JJ Masson Ben McIntosh Damien Szerszinski Twitter: http://twitter.com/moulds Instagram: https://www.instagram.com/stevemouldscience/ Facebook: https://www.facebook.com/stevemouldscience/ Buy nerdy maths things: http://mathsgear.co.uk/