How Ice Crystals Build Halos

A halo is an optical phenomenon from light interacting with ice crystals. These crystals behave like prisms and mirrors.

The ice crystals float 5–10 kilometers up in cirrus clouds. Diamond dust is a terrible engagement ring.

Hexagonal plate crystals cause light pillars when the Sun is within 6 degrees of the horizon.

The twenty two degree halo forms a large ring around the Sun or Moon. The Sun prefers its personal space.

The earliest experimental studies on halo phenomena began then.

On 20 April 1535, white circles and extra suns filled the sky for two hours. Someone painted it.

Before meteorology existed, halos were weather lore. The cirrostratus clouds causing them often meant rain within 24 hours.

You can build artificial halos using a single water glass.