Mention rainbows, and the image that comes to mind is of a beautiful translucent brightly colored arc leaning towards the horizon. But in a recent image captured by Italian astrophotographer Marcella Giulia Pace and shared by NASA on March 11, 2022, the rainbow has turned upside down – making it look like it’s smiling! As magical as it may seem, the reason for the stunning phenomenon, called circumzenithal arc, is rooted In science.
How are rainbows formed?
As you may already know, white light is made up of seven colors, namely purple, indigo, blue, green, yellow, orange and red. When a beam of white light in the air met a more dense medium, such as glass or water, it begins to move more slowly, causing it to change direction or refract. Since Components have different wavelengths, they refract, or bend, to disparate speeds. This causes the white light to come out from the medium into its making up colors.
Rainbows form when white light from the sun comes into contact with raindrops and refracts into the gorgeous bands of bright colors we are used to to have. Red has the longest wave length and bends the least. Therefore, it always appears on the outer ring of the rainbow. Violet, which has the shortest wavelength, bends the most, becoming the innermost color. Rainbows form complete circles but are only visible like semicircles from the ground because the horizon cut the other half.
What makes a rainbow “smile”?
Circumzenithal arcs, or inverted rainbows, occur when the sunyou met ice crystals inside wispy, high altitude cirrus clouds. The upside down rainbow is seen when the light beam enters through the flat upper face of the six-sided ice crystal and exits from one of its prism-like the side surfaces.
Meteorologists say that while circumzenithal arcs are fairly common at high altitudes, they are difficult to see due to low cloud. Smiling or not, the translucent band of bright colors arching perfectly on the countryside brought joy to people of all ages.
Resources: NASA.gov, BBC.com, Wikipedia.org, Earthsky.org
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