WHEN IS A RAINBOW NOT A RAINBOW? At
this time of year, a colorful arc often appears in the noontime sky.
It looks like a rainbow, but it's not. "I saw one on June 23rd while I
was walking through forest near Flagstaff, Arizona," reports David
Blanchard, who took this picture through the treetops:
Blanchard witnessed a circumhorizon arc--a
rainbow-colored band of light caused by the sun shining
through plate-shaped ice crystals floating in cirrus clouds.
Actual rainbows, on the other hand, are caused by sunlight reflected
from raindrops.
spaceweather.com
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