A while ago Christian Perfect suggested the monthly local Maths Jam organisers might write up what happens at Maths Jams to their blogs so others can get a feel for what goes on. I regard this as a good idea I haven’t got around to yet.

Luckily, Christian has just made a video showing a card trick we have played with at the Nottingham Maths Jam, so that makes this an easy post!

I was shown this trick by Matt Parker in a hotel bar in Coventry, who refused to say how it works. I went to the Nottingham Maths Jam in November 2011 having worked out how to do the trick but having spent no time at all considering how it might work, saving this for Maths Jam. I showed John Read, Kathryn Taylor and Sharon Evans and together we worked out the details given in Christian’s video.

I made a joke on Twitter based on Gauss’ reaction to Bolyai’s work on non-Euclidean geometry: “Enjoying video by @christianp. However, ‘to praise it would amount to praising myself’ ;)”. Gauss is reported to have written to Bolyai’s father:

To praise [Bolyai’s work] would amount to praising myself. For the entire content of the work … coincides almost exactly with my own meditations which have occupied my mind for the past thirty or thirty-five years.

while privately writing to a friend to say:

I regard this young geometer Bolyai as a genius of the first order.

Of course, by invoking the former I meant to imply the latter. Perhaps a more suitable quote might be that of Kelvin, having first read George Green’s Essay on electricity and magnetism:

I have just met with Green’s memoir, which renders a separate treatise on electricity less necessary… I have, most unwittingly, trodden almost exactly in his steps as far as regards electricity.

I’d say playing around with tricks and working out how they work is a very Maths Jam activity so anyone considering attending one should regard this as very much the sort of thing that happens at a Maths Jam. Find your local one, or set one up!