![]() ![]() The bow gradually faded, disappearing a full 19 minutes after sunset, with the Sun nearly ![]() We were equally amazed to see a double rainbow companion with Alexander’s dark band in between, as well as at least a first-order supernumerary bow associated with the primary bow, all of which glowed red. But as the minutes ticked away, so too did all colors except for red. As the display faded, we turned and saw a partial red rainbow in the east.Īt first, a hint of yellow-green could be seen right after sunset. My wife, Deborah Carter, and I went outside to enjoy a postsunset sky infused with fiery hues. On occasion, a red rainbow can form with the Sun a few degrees below the horizon - and that is what occurred in Maun, Botswana, on January 9, 2020. To see the phenomenon then, an observer needs to be between a low red Sun and a rain shower looming in the opposite direction. The lower the Sun is in the sky, the higher the rainbow, and vice versa. As Dutch astronomer Marcel Minnaert explains in his classic The Nature of Light and Color in the Open Air, “Nature is here showing us the spectrum of the sunlight, and demonstrating how its composition changes during sunset.” The cause is the scattering of the shorter wavelengths (by air molecules, dust, and aerosols) during light’s long trek into the lowest and densest part of Earth’s atmosphere.īecause only a setting or rising red Sun will cause a red rainbow in the opposite part of the sky, we see the bow at or near its maximum height above the horizon, 42°. Red rainbows arise from the same atmospheric conditions that cause the Sun to change its color from white to red as it sinks from a more lofty perch to within about a degree of the horizon. On the contrary, a monochromatic rainbow is a sight arguably more glorious than the more common technicolor wonder itself, chiefly because it’s red. While this is typical, rainbows can, under certain conditions, be monochromatic. Rainbows, those bridges of prismatic wonder, have enchanted observers since biblical times - although the poet John Keats apparently blamed Sir Isaac Newton for abolishing the rainbow’s poetry by reducing the sight to a strict code of color. ![]()
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