Athermancy

Part of speech: noun

Definitions

1. The quality of a substance that blocks or fails to let radiant heat pass through it
2. The property of a material being impervious to heat rays, so that thermal radiation cannot travel through it
3. Resistance of a body to the passage of infrared or radiant heat, meaning it stays opaque to thermal energy

Etymology: Athermancy is the property of being impervious to heat radiation, the capacity of a substance to block or absorb radiant heat rather than letting it pass through. The term is a scientific coinage built from Greek roots: "a-", meaning "not", and "thermansis", from "therme", meaning "heat". Its partner adjective, athermanous, is the form it is built on, and the noun was formed by adding the suffix "-y" to make a name for the quality itself. The opposite quality has its own name, diathermancy, from the Greek "dia", meaning "through", so a diathermanous substance lets heat pass through it. The pairing shows how physicists sorted materials by how they handled radiant heat: some stop it, some transmit it. Glass, for instance, transmits much visible light while blocking many infrared wavelengths, which is why it behaves in ways that depend on the wavelength involved.

Antonyms: diathermancy