What is an Ames Test? How engineered Salmonella strains are used to work out whether a drug candidate causes mutations in our DNA. Kahn's Algorithm In-degrees, adjacency lists, and how Kahn's algorithm peels a directed graph into a topological order one dependency-free layer at a time. Thoughts on EdTech Notes from two After Babel articles on how phones and device-based learning have actually played out in American schools. The hard thing about hard things You rarely know you are in the middle of a hard thing while it is happening, and that missing bit of knowledge is what decides whether you keep going. Books I recommend The handful of books I reach for whenever someone asks me for a recommendation.