Last Wednesday, an extraordinary optical phenomenon was observed in the US state of Massachusetts. An unusual rainbow cloud appeared in the sky.
The phenomenon aroused great interest and was widely commented on. Most people have seen something like this for the first time in their lives.
In meteorology, such an unusual fire rainbow is named after a horizontal arch. It is one of the species of solar halo. This effect causes iridescence and it arises when a strong source of light hits a fragment of a cloud containing a lot of ice crystals, acting like miniature prisms.
