April 05, 2016 at 11:49PM

Tody I Learned: 1) There is a scientific definition of a pebble, as a shape -- it's a 3D solid for which the curvature* of points around the surface has a normal (Gaussian) distribution. That is, if you sample random points on the outside of a pebble and measure the curvature of each point, and make a histogram of those curvatures, you get a normal distribution (bell curve). *Also, today I learned the definition of curvature, at least on a plane. The curvature of a point on a plane is one divided by the radius of a circle you could make that would snugly hug the plane at that point. The idea is that as the radius of the circle gets bigger (and the curvature gets smaller), the edge of the circle gets flatter and flatter. Credit for these two facts goes to Mengsha Gong. Thanks Mengsha! 2) Ants get their pheromonal boquets from the queen, especially in a young colony. The ants that attend to the queen pick up her scent, and as they share food and grooming, they spread it around the colony. This means that you can take pupae from another colony, and if you can get them to survive and be groomed in the nest for long enough, they pick up the queen's scent and are treated as members of the colony. Conversely, if you take those ants and reintroduce them to their mothers' colony, they will be rejected as foreign. This suggests a somewhat risky tactic for supplementing young queens' retinues if you have a breeding hive of the same species. Getting new workers in a young colony is critical for the colony's stability. I'm not sure if any special treatment would be required to keep the larvae safe, but it seems worth a try. 3) Polytetrafluoroethylene (PTFE, also known by the brand names Teflon and Goretex) is ridiculously safe stuff. Item 1: PTFE is used to coat stents, and is not obviously toxic or dangerous (http://ift.tt/1V8eBra and http://ift.tt/1SOGQYA for a couple of different perspectives -- it's not clear whether or not they're better than bare-metal stents, but they're ceratinly not overtly toxic). Item 2: Rats fed a diet of 25% PTFE for 90 days showed no signs of toxicity or damage (http://ift.tt/1V8eEmN). That's ridiculous. What about Teflon cookware? Well, PTFE itself is pertty damned stable at cooking temperatures, but there are chemicals in old teflon cookware involved in sticking the teflon to the actual pan that could volatilize and potentially cause some respiratory damage. Bonus: A dialectic, in the classical, Socratic sense (as opposed to the Hegelian sense) is a discussion in which two people with different opinions argue in order to figure out the truth. I really, really should have already known this, and now I do thanks to Eliza Dickinson Urban!