> (Note: Glass windows are opaque to thermal cameras; the temperature measured here is the surface temperature of the window.) This is not completely correct.

> (Note: Glass windows are opaque to thermal cameras; the temperature measured here is the surface temperature of the window.) This is not completely correct. Glass tends to reflect infrared radiation. For example if you view a car windscreen from the air with a thermal camera, you'll see a reflection of the sky. It's more complicated than that, because you'll also detect the emitted blackbody radiation from the glass (for whatever temperature).