Shimmering Pink Sunrise

by Greni Graph

Title

Shimmering Pink Sunrise

Artist

Greni Graph

Medium

Photograph - Photography

Description

Sunrise or sun up is the instant at which the upper edge of the Sun appears on the horizon in the morning. The term can also refer to the entire process of the sun crossing the horizon and its accompanying atmospheric effects. Although the Sun appears to "rise" from the horizon, it is actually the Earth's motion that causes the Sun to appear. The illusion of a moving Sun results from Earth observers being in a rotating reference frame; this apparent motion is so convincing that most cultures had mythologies and religions built around the geocentric model, which prevailed until astronomer Nicolaus Copernicus first formulated the heliocentric model in the 16th century. Architect Buckminster Fuller proposed the terms 'sunsight' and 'sunclipse' to better represent the heliocentric model, though the terms have not entered into common language. Air molecules and airborne particles scatter white sunlight as it passes through the Earth's atmosphere. This is done by a combination of Rayleigh scattering and Mie scattering. Pure sunlight is white in color, containing a spectrum of colors from violet to red. When sunlight interacts with atmospheric particles much smaller than the wavelength of visible light, a phenomenon known as Rayleigh scattering occurs. In this process, light is scattered in various directions, with shorter wavelengths (violet, blue, and green) being scattered more strongly than longer ones (orange and red). Because of this effect, the Sun generally appears yellow when observed on Earth, since some of the shorter wavelengths are scattered into the surrounding sky. This also makes the sky appear increasingly blue farther away from the Sun. During sunrise and sunset, the longer path through the atmosphere results in the removal of even more violet and blue light from the direct rays, leaving weak intensities of orange to red light in the sky near the Sun. The intense reds and peach colors in brilliant sunrises come from Mie scattering by atmospheric dust and aerosols, like the water droplets that make up clouds. We only see these intense reds and peach colors at sunrise and sunset, because it takes the long pathlengths of sunrise and sunset through a lot of air for Rayleigh scattering to deplete the violets and blues from the direct rays. The remaining reddened sunlight can then be scattered by cloud droplets and other relatively large particles to light up the horizon red and orange. These larger particles, with sizes comparable to and longer than the wavelength of light, scatter light by mechanisms treated by the Mie theory. Mie scattering does not depend heavily on wavelength, but it has the largest effect when an observer views the light directly (such as toward the Sun), rather than looking in other directions. Mie scattering is responsible for the light scattered by clouds, and also for the daytime halo of white light around the Sun (forward scattering of white light). Without Mie scattering at sunset and sunrise, the sky along the horizon has only a dull-reddish appearance, while the rest of the sky remains mostly blue and sometimes green. Ash from volcanic eruptions, trapped within the troposphere, tends to mute sunset and sunrise colors, whereas volcanic ejecta lofted into the stratosphere (as thin clouds of tiny sulfuric acid droplets) can yield beautiful post-sunset colors called afterglows and pre-sunrise glows. A number of eruptions, including those of Mount Pinatubo in 1991 and Krakatoa in 1883, have produced sufficiently high stratospheric sulfuric acid clouds to yield remarkable sunset afterglows (and pre-sunrise glows) around the world. The high-altitude clouds serve to reflect strongly-reddened sunlight still striking the stratosphere after sunset down to the surface. dakota, light, photography, shimmer, pink, sunrise, black hills, south dakota #201301166371

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January 18th, 2013

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