I'm going to start this post by saying I'm not a regular reader of the xkcd comic strip (a humorous stick figure comic strip about science, technology and maths).
But I have friends who love it, and post some of the hi-lights on their Facebook/Twitter streams. It was in that way that last week I stumbled across the below. Which obviously had to be posted here (click on the image to visit it on the xkcd website).
