How Things Work on Instagram: "Some outdoor cameras and sensors use spinning lenses or spinning glass covers to keep working in extreme weather, and the principle is simple: fast rotation throws water, snow, dust, and mud outward using centrifugal force. The spinning element—usually a thin, optically clear disk—sits in front of the actual lens and is driven by a small motor. When it spins at high speed, anything landing on it gets flung off instantly, preventing droplets or debris from sticking