Hilary Mason, chief scientist at bitly, examined links to 600 science pages and the pages that those people visited next:
The results revealed which subjects were strongly and weakly associated. Chemistry was linked to almost no other science. Biology was linked to almost all of them. Health was tied more to business than to food. But why did fashion connect strongly to physics? And why was astronomy linked to genetics?
The interactive lets you poke around the data, looking at connections sorted from weakest (fewer links) to strongest (more links), and nodes are organized such that topics with more links between each other are closer together.
Natural next step: let me click on the nodes.