Thermometry at the mK scale, revisited

It's been almost a decade since I last wrote about this topic , and a preprint on the arXiv this week is a good jumping off point for more discussion. Thermometers are devices that allow us to take some physical observable and infer temperature. I wrote about the nature of temperature 17 years ago (!!!) in a way that did not completely satisfy me or most of my readers, so maybe I should take…