Atmospheric Whys Behind Spectacular Skies

Sun on the horizon. Photo courtesy of Johannes Plenio on coolfreepix.

I can hardly turn away from this spectacular sunset. Except for the sun on the horizon, I can’t tell where sea ends and sky starts. “Spectacular” comes from the Latin spectaculum meaning “a sight, show,” and the sky in this picture is certainly that. What’s going on here to produce such a breathtaking blend of color?

It has much to do with the gases, dust, and water droplets that make up the atmosphere. They scatter the Sun’s rays as it travels from the distant horizon to the fishermen’s eyes. Remember that sunlight includes every color of the spectrum, from violet and blue at one end to yellow, orange, and red at the other. Colors toward red scatter less as their wavelengths are longer. By the time the sunlight reaches the fishermen, violets, blues, and greens have been scattered and absorbed more than the other colors. The duo see mostly yellows, oranges, and reds.

Depending on the content and size of the particles in the air, the fishermen sometimes spot pinks and purples. Extra fine sulfurous dust from a volcano in one part of the world can lead to a staggering sunset thousands of miles away.

Photo by Johannes Plenio at coolfreepix.

Image courtesy of Quang Le on Pixabay.
Photo by Cindy Lever from Pixabay.

If particles in the air are too large, they dull the display. But if they’re fine enough, they amplify the beauty.

Sunset in Montreux, Switzerland. Photo by Artiom Vallat on Unsplash.

If our fishermen go for a hike, they might see the blue-tinted vapor, or haze, that often develops over heavily forested areas due to the natural emission of organic gases from the trees. Blue haze famously envelops the Great Smoky Mountains in the United States, but it can happen anywhere with abundant trees and plants. Blue haze intensifies when humans release sulfur dioxide into the air, which happens with the burning of fossil fuels, especially from older-style coal-burning power plants. Too much blue harms both plants and people.

Blue haze over the Blue Ridge Mountains in the United States. Image by Dr. Michael A. Milton from Pixabay.

Photo of the Great Smoky Mountains by Micah Williams on Unsplash.

Our fishermen/hikers would certainly notice these sunbeams on their journey. Beams are another example of sunlight scattered by air molecules or particulates like smoke and dust.

Photo by Martin Winkler from Pixabay. Interestingly, the beams are parallel to each other and do not converge on a single point, despite what our hikers’ minds tell them. Imagine how parallel railroad tracks appear to converge on a faraway point. It’s an illusion.

Fog is ideal for sunbeams.

Image by Couleur from Pixabay.

Midway through their journey, our fishermen/hikers settle in for a night’s rest. They might see a Supermoon, when the Moon is both full and near the closest point in its orbit around Earth (called perigee).

Supermoon image by Michael Just from Pixabay.

Or, before drifting off, they might see a smaller Micromoon, when a Full Moon is close to apogee, or its furthest point. Full moons show up 12 or 13 times a year and three or four of those are either super or micro.

Image courtesy of NASA/JPL-Caltech on Wiki Commons.

Eventually, our fishermen return to their boat, just in time for a spectacular sunrise.

Sunrise back on their boat. Photo of Da Nang Bay, Vietnam, by PublicDomainPictures on Pixabay.

Works Cited

“Atmospheric Optics.” Wikipedia.

“Blue Skies and Red Sunsets.” The Physics Classroom.

Corfidi, Stephen F. “The Colors of Sunset and Twilight.” NOAA/NWS Storm Prediction Center. Sep 2014.

Fiegl, Amanda. “Red Sky at Night: The Science of Sunsets.” National Geographic. 29 Oct 2013.

Funk, Ted. “Cloud Classifications and Characteristics.” The Science Corner.

“Micro Moon–What is a Micro Moon?” Full Moon Phases.

Phillips, Dr. Tony. “Why Are Sunsets Turning Purple?” Space Weather Archive. 27 Aug 2019.

“Rays and Shadows.” Atmospheric Optics.

“Sunbeam.” Wikipedia.

“Sunrays-Crepuscular rays.” Atmospheric Optics.

“Supermoon.” Wikipedia.

Texas A&M University. “Going Green On Hold: Human Activities Can Affect ‘Blue Haze,’ World’s Weather.” Science Daily. 12 Oct 2009.

“Why is the Sky Blue?” Atmospheric Optics.

Williams-Rice, Mike. “Coal Power Regulations Neglect Sulfur Dioxide Danger.” Futurity. 1 Nov 2018.

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