Here is the first of my fall This Week's Finds lectures!   In it, I explain the idea of categorification: taking math that uses sets, and replacing these sets by categories.   Then I explain what happens when you categorify the idea of 'category'.

The quality of the video starts out being pretty bad - my poor pal Tom Leinster had to learn how to use a new camera on the fly: the old one broke due to a 'firmware update'.   But apparently adjustments in the lighting made things a bit better after a while.   Also someone found some white chalk instead of yellow chalk.

The talk didn't get as far as I wanted - among other things, someone started drilling in the room above, and Neil Turok had to run upstairs to tell them to knock it off.

Sigh.

https://www.youtube.com/watch?v=ZVecriTCBLU 

 @b4c50e1b It’s unreal how many things can go wrong when trying to record a lecture. One trick I’ve learned is to actually make the recording in advance while preparing for the live version. It takes a bit more time that way but it’s much less stressful and gives more of a chance to troubleshoot issues. 

 @b4c50e1b Nice picture of the associahedron! 😉