10 stunning images of rainbows and their less-famous cousins
By Mother Nature Network, 24 September 2012.
By Mother Nature Network, 24 September 2012.
We tend to associate rainbows with myth because they call to us with the promises of riches. But rainbows are not the only masterpieces that nature paints across the sky. There are also moonbows, triple sunrises and even fog bows that arch over the horizon. Here are 10 impressive images of rainbows and their cousins. (Text: Katherine Butler)
1. At the end of the rainbow
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2. Reflection and refraction
Strictly defined, a rainbow is a band of colours formed by the reflection and refraction of the sun’s rays inside raindrops. But regardless of the science, there is an element of the fantastic to rainbows. While their colours include red, orange, yellow, green, blue, indigo and violet, they are also made up of an infinite range of hues that the human eye cannot see. Rainbows can appear as multiples or even appear without colour at all. If you can see the shadow of the back of your head after a storm, you are very likely to look up to a rainbow as well. Pictured here are a rainbow and its reflection over Malmesjaur in Moskosel, Lappland Sweden, as photographed on July 14, 2009.
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3. The colours of the rainbow
At the same time, a rainbow truly is an individual experience. We see rainbows because the sun is behind us, reflecting sunlight off the rain, waterfall, mist, dew, or even a water fountain that is before us. But everyone sees their own individual rainbow according to their particular angle, light, and how their eyes interpret colour. Combined, colours look white. Refracted, they are broken up into the blues, reds, and oranges we know. Pictured here is a double rainbow just before sunset over Castle Cornet, Guernsey, Great Britain. Double, or secondary, rainbows form when a beam of light is refracted twice.
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4. The colour of order (and order of colour)
A rainbow forms when each tiny droplet of water disperses sunlight. The pattern of light is always the same in a primary rainbow because each colour is reflected at its own particular wavelength. In a primary rainbow, the colours will be in the order of red, orange, yellow, green, blue, indigo and violet. Or ROYGBIV. Red has the longest wavelength, with each colour decreasing away from it. The colours seem to blend into each other because the light exits at different angles, rather than one unmoving angle. Here we see a supernumerary rainbow, an infrequent phenomenon that happens when faint rainbows are seen within the inner ring of a primary rainbow. Experts say that geometric optics does not fully explain the existence of supernumerary rainbows, which are likely created due to the varying wave nature of light.
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5. Six rainbows across Norway
Photo: NASA/Terje O. Nordvik
When does the colour scheme ROYGBIV get reversed? This will never happen in the primary rainbow, but a reflection might reverse the order of colours. NASA explains it this way: “multiple internal reflections inside water droplets sometimes make a secondary rainbow to become visible outside the first, with colours reversed.” Pictured here are multiple rainbows photographed in Norway on Sept. 12, 2007. The third rainbow (the one in between the primary and secondary ones) was caused by sunlight that had first reflected off the lake, according to NASA. If you look into the lake itself, you'll see three more reflections of rainbows.
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6. A rainbow for fear or fantasy?
There are many different kinds of rainbows. In addition to a primary rainbow, which is the most commonly seen, there are also secondary rainbows that occur when two reflections take place in a water droplet. Then there is the monochrome rainbow. These happen at sunrise or sunset, when the shorter blue and green wavelengths are scattered out before they reach the water droplets. Hence, the human eye sees only red. This unenhanced image was taken on July 6, 1980, just outside of Minneapolis, Minnesota [USA].
7. The glory of a circular rainbow
Photo: NASA/Raquel Yumi Shida
A rainbow gets its traditional semicircle shape from the horizon, which makes it seem as if it is half a circle. So when the same atmospheric conditions that create a rainbow are observed from an airplane, a rainbow can appear to be a full circle. This is called a glory, which NASA defines as an optical phenomenon that “looks like small, circular rainbows of interlocking colours.” This glory was photographed from a plane over South Africa.
8. Triple sunrise over Wisconsin
Photo: NASA/Jim Hoida
Rainbows aren’t the only atmospheric delights. Here we see a triple sunrise as photographed near Green Bay, Wisconsin [USA], on Sept. 23, 2006. This was when the sun was rising due east on the Equinox. But these weird apparitions are actually more common than rainbows. “Produced by sunlight shining through common atmospheric ice crystals with hexagonal cross-sections,” NASA writes, “such halos can actually be seen more often than rainbows.” The two images on the right and left of the central sunrise are sundogs, which are extra-images of the sun created by falling ice crystals in the atmosphere.
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9. A fog bow over California
Photo: NASA/Mila Zinkova
Not all arches in the sky are filled with colours. Here we see a fog bow arcing over the Golden Gate Bridge in San Francisco, California [USA], on Nov. 15, 2006. The principle of formation for a fog bow is similar to a rainbow, as the fogbow is a reflection of sunlight. However, as NASA describes it, the lack of relative colours are due to the relatively smaller water drops. “The drops active above are so small that the quantum mechanical wavelength of light becomes important and smears out colours that would be created by larger rainbow water drops acting like small prisms reflecting sunlight,” writes NASA. The right end of the fog bow appears to dip right into the top of the Golden Gate Bridge.
10. Moonbow with sailboats
Photo: NASA/Matt BenDaniel
Pictured here is a moonbow, also known as a lunar rainbow, as imaged on July 4, 2001, near Salt Pond Bay in St. John, Virgin Islands. Moonbows operate on the same principles as rainbows; however, they are possible because of the light of the moon instead of the sun. As moonlight is simply reflected sunlight, the colours of a moonbow are the same as a rainbow. Accordingly, as the sun is much brighter than the moon, moonbows are much fainter and rarer than rainbows. While they usually look white to the human eye, their colours can be discerned in long exposure photos.
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