● A Yellow Dusk
▘ "A yellow dusk" is a phenomenon caused by atmospheric scattering of sunlight, where shorter, blue wavelengths are dispersed, leaving longer, yellow, orange, and red wavelengths to reach our eyes.
▘ The colors of the sunset result from a phenomenon called scattering, says Steven Ackerman, professor of meteorology at UW–Madison. Molecules and small particles in the atmosphere change the direction of light rays, causing them to scatter.
▘ Scattering affects the color of light coming from the sky, but the details are determined by the wavelength of the light and the size of the particle. The short-wavelength blue and violet are scattered by molecules in the air much more than other colors of the spectrum. This is why blue and violet light reaches our eyes from all directions on a clear day. But because we can’t see violet very well, the sky appears blue.
▘ Scattering also explains the colors of the sunrise and sunset, Ackerman says.
▘ “Because the sun is low on the horizon, sunlight passes through more air at sunset and sunrise than during the day, when the sun is higher in the sky. More atmosphere means more molecules to scatter the violet and blue light away from your eyes. If the path is long enough, all of the blue and violet light scatters out of your line of sight. The other colors continue on their way to your eyes. This is why sunsets are often yellow, orange, and red.”
▘ And because red has the longest wavelength of any visible light, the sun is red when it’s on the horizon, where its extremely long path through the atmosphere blocks all other colors.
▘ As the storm clears, the low-angle sunlight, especially near sunset passes through water droplets, dust, and clouds, scattering shorter blue wavelengths and allowing more yellow, orange, and red hues to dominate. The result: an eerie yellow glow across the sky.
▘ Three Types Of Dusk?
▘ However, technically, the three stages of dusk are as follows:
At civil dusk, the center of the Sun's disc goes 6° below the horizon in the evening.
▘ At nautical dusk, the Sun moves to 12° below the horizon in the evening.
▘ it does not do to dwell on dead things,
past the bloom of their changes, and flowers today
all reek. I find you hidden among them, O
my corpse flower, and if the mammals desert you,
let them. the flesh flies will arrive soon
to pester you with unrelenting praise
▘ A sloth, climbing a large mound atop which blooms a rose, arrives at the summit, and— « Something has happened; it is up to us to name it, or not to. Something is wrestling us for our blessing » (Cavell). What has happened? It is not clear. An atom, falling through the void, swerves. Deep underground, a coal fire burns for decades. A red triangle spins in a dense fog. Long ago, an obscure entomologist discovers a spurious pattern in the classification of scarabs. The sun, making its daily journey, arrives at Anxiety Abyss, and this, we are told, is called Yellow Dusk. The poem spans this abyss.
▘ At astronomical dusk, the Sun's position is 18° below the horizon in the evening.
▘ Sunlight is white (a mix of all visible wavelengths) at its source; the color you perceive depends on which wavelengths reach your eye after traveling through Earth's atmosphere.
▘ The apparent shift from yellow midday to orange/red at dawn and dusk is explained by scattering, path length, and human perception:
▘ Rayleigh scattering and wavelength dependence
▘ Air molecules and very small particles scatter shorter wavelengths (blue, violet) far more strongly than longer wavelengths (red, orange).
▘ Scattering efficiency ∝ 1/λ^4, so blue light is removed from the direct beam much more than red as sunlight passes through air.
Optical path length (air mass)
▘ At noon the Sun is high; sunlight travels a short path through the atmosphere. Most wavelengths survive, so the direct sunlight reaching your eye is close to white with a slight yellow cast because the human eye and atmospheric ozone/absorption reduce some violet/blue.
▘ At sunrise/sunset the Sun is near the horizon; the beam traverses a much longer path through the atmosphere. Much of the blue/green light is scattered out of the direct beam, leaving proportionally more red and orange.
▘ Additional scattering and particles
▘ Aerosols, dust, smoke, pollution, and water droplets scatter and absorb light differently from molecules (Mie scattering). These larger particles scatter more evenly across wavelengths and can enhance reds/oranges by removing mid‑short wavelengths or by forward-scattering the reddened beam.
▘ After volcanic eruptions or during wildfire smoke events the sky often looks extra-red because additional particles increase scattering and absorption of shorter wavelengths.
▘ Human vision and contrast effects
▘ Human color perception depends on surrounding light and contrast. Against a bluish or dim background sky, the remaining warm wavelengths from the Sun look more intensely orange/red.
Low light levels at dawn/dusk reduce cone sensitivity; rods dominate for a time, shifting perceived color balance and making hues appear richer when cones again respond.
▘ Optical path phenomena that intensify colors
▘ Tropospheric refraction and multiple scattering can change the Sun’s apparent size and color gradients.
▘ Clouds or haze near the horizon can filter light like a colored filter, deepening oranges and reds.
▘ Net result: midday Sun looks yellow because little blue light has been removed; dawn/dusk Sun looks orange/red because the long atmospheric path preferentially removes blue and green wavelengths, leaving longer (red/orange) wavelengths and altering perception through contrast and particle effects.
▘ The Earth’s atmosphere scatters blue light (shorter wavelengths) more efficiently than it scatters red light (longer wavelength). When the Sun is high in the sky its light passes through less atmosphere, so less light is scattered. When the Sun is near the horizon, the light passes through more miles of atmosphere, and more of the blue light is scattered, leaving the Sun looking red.
▘ The sun is orange near the horizon because the blue gets scattered. This even happens in clear air, and the scattered blue light is what makes the rest of the sky blue - You are seeing the scattered blue light. On clear days far from cities the sun only looks orange as it gets very close to the horizon when its light passes through a lot of air due to the low angle.
▘ But particles in the air also tend to scatter blue light, making the sun look orange. Years ago, after Mt St. Helens erupted half a continent away the sun looked orange throughout the entire day.
▘ So why might the afternoon sun look more orange than the morning sun? In some cities there are cars, trucks, power plants, and other industry that emit far more pollution during the day than they do overnight. So while the local level of air pollutants is low in the early morning, that level is higher by late afternoon, leading to more scattering of sunlight. Furthermore, sunlight itself causes the existing air pollutants to chemically react, turning them into other chemicals that scatter sunlight even more effectively, so they build up by late afternoon, but are mostly absent in the morning.
▘ Introducing Yellow Dusk
▘ A bold new hue for summer’s quiet thrill
▘ That endless summer feeling—light-drenched, slow, a little aimless. Days drift by in a golden blur, quiet and warm, stretched out by the pool or under the trees. But beneath the stillness, something stirs. A promise of the unknown.
▘ Dusk Yellow, radiant and free-spirited, belongs to this moment between afternoon and evening—bold, luminous, and made for the thrill of what might happen next.
▘ Why Is Yellow So Prominent in Van Gogh’s Paintings?
▘ Vincent van Gogh painted what were destined to become his most famous works in sun-drenched Arles: Sunflowers, The Bedroom, The Yellow House and the sweeping landscapes with wheat fields, sowers and reapers under the shimmering sun.
▘ That’s what you associate with Van Gogh, what gets etched in your memory – all that yellow, used to portray the southern light and way of life.
▘ But Van Gogh naturally used plenty of other colours. Consider the paintings from his Dutch period, where he primarily used browns, greys and greens. Or his Parisian works, where his palette became noticeably lighter and brighter.
▘ Van Gogh Watercolour Dusk Yellow 230 is a semi-opaque, dark greenish yellow color with excellent lightfastness and granulation capabilities.
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