30 September 2014
The Short Answer (TSA)
The light
of the sun makes rainbows. The light of
the moon makes moonbows. The basic
principle at work in a rainbow and moonbow are the same. Really small droplets of water in a really
moist -- almost cloudy --- sky split (or “refract”) the white light of the sun
or moon into the colors of a rainbow or a moonbow.
Rainbows are common. But moonbows are rare because the moon isn’t nearly as bright as the sun. In perfect conditions, it takes all the sunlight reflected by a full moon to make a moonbow. Even then, the low light of the moon may not be able to make a rainbow of colors, but only a faint white arch.
Rainbows are common. But moonbows are rare because the moon isn’t nearly as bright as the sun. In perfect conditions, it takes all the sunlight reflected by a full moon to make a moonbow. Even then, the low light of the moon may not be able to make a rainbow of colors, but only a faint white arch.
If a
moonbow appears at all, it will always be faint. And moonbows always appear in the opposite side
of the sky from the moon. “Moonbow”
isn’t the only name given to rainbows made by moonlight. Sometimes, a moonbow is called a lunar
rainbow, black rainbow, white rainbow, lunar bow, or space
rainbow. At least, this is what a “true”
moonbow is called. There are also
“false” moonbows.
What are
these mysterious things appearing in the sky and pretending to be
moonbows? Well, a "false" moonbow is
formed when the moisture in the air isn’t natural, but geological.
What does that mean?
What does that mean?
If the
moisture that makes the moonbow doesn’t come from natural weather conditions, it's a "false" moonbow. So, if the spray, mist or fog that makes the moonbow is from from a waterfall, the moonbow is a “false" one. “False” moonbows are
easy to photograph because they are almost always visible at certain places
such as Yosemite Falls in California, Cumberland Falls in Kentucky, and
Victoria Falls in Africa.
There’s a
way to tell if a moonbow is “false.”
Watch and see what happens after the moon sets, and the sun rises. If the arching band of colors is always there
– day or night -- it’s “false." After
the moon sets, the moonbow fades away.
But the mist from a large waterfall is always there. So, as soon as the sun rises, a rainbow will
appear. Well, actually, a “false”
rainbow will appear. The sun picks up
where the moon left and off. But when
made by the mist of a large waterfall, both the nighttime moonbow and daytime
rainbow are “false.”
By the way,
true moonbows are rare and hard to photograph.
So, there aren’t so many pictures of true moonbows. But “false” moonbows are a lot easier to find
and predict. So, again, most photographs are of "false" moonbows.
M Grossmann of Hazelwood, Missouri
& Belleville, Illinois
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