thumb|upright=1.4|The Amazon River delta showing no clouds above river waters because water is not a diathermanous fluid.
thumb|upright=1.4|The Amazon River delta showing no clouds above river waters because water is not a diathermanous fluid.
Diathermancy (from "dia" through and "thermē" heat) is the property of some fluids that allows rays of light through them without itself being heated. A diathermanous substance is thus "permeable" by heat. Diathermancy was first described by German physicist and chemist Heinrich Gustav Magnus in the 1800s.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).