space@mit-mc (03/02/85)
From: Dick Koolish <koolish@bbncd2.arpa> Crookes radiometer does not work by light pressure. The globe contains a low pressure gas. The incomming light heats up the dark side of the vanes. When a gas molecule hits the dark vane, it absorbes some of the heat and rebounds faster than if it hit the cool silvered side of the vane. This is what makes the vanes turn.