Paul holds a mask he made from a face cast. The cast is convex from one side and concave from the other. The interesting thing is that you can't tell by looking at it which is which. Click on the image to read more about this optical illusion.
Paul performs an experiment of crushing a beer can by creating a vacuum inside. Click on the image for a link to a video of the experiment.
Annie caught at a dramatic moment. I don't remember now what this was about.