What governs the speed at which raindrops fall, sediment settles in river estuaries, and matter is ejected during a supernova? These questions circle around one, deceitfully simple factor: the rate at ...

March 17, 2026 • US-Israeli airstrikes on oil depots culminated in ‘black rain’ in Iran early last week – a phenomenon usually caused by large amounts of soot, carbon and other pollutants in the air.