Have you ever seen a halo around the Moon?
This fairly common sight occurs when high thin clouds containing millions of tiny
ice crystals cover much of the sky.
Each ice crystal acts like a miniature lens.
of the crystals have a similar
elongated hexagonal shape,
light entering one crystal face and exiting
through the opposing face refracts 22 degrees,
which corresponds to the radius of the Moon Halo.
may be visible during the day.
The setting of the
above picture is
The distant planet
appears by chance on the
how ice-crystals form
in clouds remains under