A day doesn’t pass without people posting colorful images of supposed sky phenomena. A rainbow over a sunrise. A halo with its bottom touching the Moon and the rest forming the letter O above. Multicolored rays streaming down from the clouds. And in the comments, people write, “amazing!” and “great photo!”
And your poor tortured friend Bob slumps in astonishment. Don’t people know even the stone-cold basics of rainbows? Or halos? Or what creates colors in the sky? The answer, sadly, is no. No wedding photographer could offer the bride a collection of images showing guests with green skin because everyone knows the correct range of possible skin tones. But atmospheric phenomena are somehow an arcane, little-known area of human knowledge.
So here’s a brief outline of how to spot web fakery in the main recurring areas that are continually posted.
• Rainbows. First, a rainbow must appear opposite the Sun. So much so, that the exact center of every rainbow’s arc is the shadow of your head. Thus you could never see a rainbow as an arch above a sunrise or a sunset. Also, pay attention to the light on clouds or mountains in the image. If sunlight is obviously coming from the left, say, the camera could not be facing a rainbow. Moreover, a rainbow isn’t a real object. It doesn’t cast shadows or have a reflection. And it must always be a perfect portion of a circle. So those computer-created images showing one side of the rainbow as thicker and seemingly nearer to the camera than the other side, which is depicted as farther away to give it a seeming dimensional “presence,” that’s automatically fake as well.
• Halos. A solar or lunar halo always precisely surrounds those objects, and is always the same 22-degree radius (except for the rare and faint 46-degree halo). So all those supposed images of a sun rising with the bottom of a halo touching it are fake. In the actual sky, an extended arm with your hand spread widely apart is a cool instrument for assessing haloes. If you put your thumb tip against the Sun, your pinky tip will just perfectly touch the halo. That’s because an extended open hand with thumb extended blocks out 22 degrees.
• Colors. The human eye is built so that it perceives white whenever the primary colors of light are present. Since light bulbs and sunlight contain equal amounts of red, blue and green, our minds see illuminated objects as being bathed in white. To get colors, some process must break apart the mixture and preferentially display only part of the spectrum. At this time of year, we see a lot of natural green because chlorophyll, botany’s major compound, absorbs red and blue light in its energy and sugar production process, but has no use for green. So the sun’s green component is rejected and reflected away, which is why grass and leaves appear that color. In dusty or very humid air, breaks in clouds let streams of sunlight through, giving us those magical-looking rays. They’re white. Or, near sunset, somewhat orange. You’ve never seen blue or green rays streaming down because there’s no process up there that is breaking apart the sunlight.
• Cloud colors. The edges of certain clouds near the Sun have droplets of varying sizes, which create diffraction, a fascinating non-refraction process that creates colors by a wave-interference process never seen in a rainbow, like aquamarine, brown and magenta. This also happens on oily roadside puddles. But such colors are not deeply saturated; they don’t “pop out” to anyone, and are better seen through sunglasses. Look for this on cloud edges and you’ll see such “cloud iridescence” weekly. But it’s a bit subtle, and bears no resemblance to the loud bright colors in those web images.
• More? A good website showing actual atmospheric phenomena is AToptics, a UK (United Kingdom) site that has a stupendous collection of actual images, rare and common. You can spend hours at this magnificent site, and come away with a much deeper appreciation of what’s really possible over your head.
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