Light is the essential source of information about the surrounding world for most of us. We see objects of di?erent brightness and colours, or, in scienti?c terms, we distinguish objects by the way they re?ect light of di?erent wa- lengths with varying e?ciency. It was exciting for both of us to learn that scienti?c instruments can expand our senses and provide information from this very same radiation that goes far beyond the simple recognition of - jects. Theabilityto see thecompositionoftheairsurroundingusandabove our heads, to us and others, one of the most fascinating aspects of the app-...