Answer · confidence: strong
Why does a hazy sky near the horizon look whiter than the sky overhead on the same day?
The records show that the overhead sky looks blue mainly because Rayleigh scattering scatters shorter blue wavelengths more strongly than longer red ones 1. Near the horizon, the light reaching the eye has travelled through about 100 miles or more of air, compared with roughly 8 miles overhead 8. Along that longer path, larger particles such as dust, pollution, and water droplets produce Mie scattering, which scatters visible wavelengths more evenly and adds a whitish component that makes the blue look paler 611. Repeated Rayleigh scattering in the dusty, humid layers near the ground also washes the blue toward white 12.
Checked 2026-10-21. Only documented and supported facts are used.
Dig deeper on this questionSources
[1] supported
Rayleigh scattering is the main cause of the blue color of the sky on a clear day, because shorter blue wavelengths passing overhead are scattered more strongly than longer red wavelengths.
"This scattering mechanism is the primary cause of the blue color of the Earth's sky on a clear day, as the shorter blue wavelengths of sunlight passing overhead are more strongly scattered than the longer red wavelengths according to Rayleigh's famous 1/ λ 4 relation."Scattering
[2] supported
The degree of scattering depends on the ratio of particle diameter to the wavelength of the radiation, along with other factors such as polarization, angle, and coherence.
"The degree of scattering varies as a function of the ratio of the particle diameter to the wavelength of the radiation, along with many other factors including polarization , angle, and coherence ."Scattering
[3] supported
Scattering by spheres larger than the Rayleigh range is usually called Mie scattering, which was first solved by Gustav Mie.
"For larger diameters, the problem of electromagnetic scattering by spheres was first solved by Gustav Mie , and scattering by spheres larger than the Rayleigh range is therefore usually known as Mie scattering."Scattering
[4] supported
Surfaces appear white because of multiple scattering of light by internal or surface inhomogeneities.
"Surfaces described as white owe their appearance to multiple scattering of light by internal or surface inhomogeneities in the object"Scattering
[5] supported
The Tyndall effect makes a medium look whitish and turbid when the scattering particles are larger than the wavelength of light.
"das Medium weißlich trüb erscheinen lassen, wenn sie größer sind."Tyndall-Effekt
[6] supported
Near the horizon, light travels through more air and particle-filled layers, so extra Mie scattering from dust and pollution adds white light and makes the blue look paler.
"Near the horizon, light travels through more air and more particle‑filled layers, so additional Mie scattering from dust and pollution adds white light and makes the blue look paler and less saturated."How Rayleigh Scattering Turns a Blue Sky Into Red/Orange Sunsets Over a Long Atmosphere Path
[7] supported
The Tyndall effect itself is not responsible for the blue color of the sky.
"Der Effekt ist allerdings selbst nicht für die blaue Farbe des Himmels verantwortlich."Tyndall-Effekt
[8] supported
Above the observer there is about 8 miles of atmosphere, while the light reaching the eye from the horizon has travelled through 100 miles or more.
"Above your head is roughly 8 miles of atmosphere, but when looking at the horizon, the light must travel through 100 miles or more of the atmosphere before reaching your eye."Sky Horizon Science: Why Is The Sky Lighter At The Horizon?
[9] supported
Looking toward the horizon means viewing through a longer path of air with more particles, and these larger particles add a whitish component that dilutes the intense blue sky.
"Looking toward the horizon means viewing through a longer path of air and more particle‑filled layers that contain dust, pollution, and droplets. These larger particles enhance Mie scattering, adding a whitish component that dilutes the intense blue sky."How Rayleigh Scattering Turns a Blue Sky Into Red/Orange Sunsets Over a Long Atmosphere Path
[10] supported
John William Strutt, 3rd Baron Rayleigh, proposed in 1899 that pure air alone, without colloidal particles, causes the scattering that makes the sky blue, the Rayleigh scattering named after him.
"John William Strutt, 3. Baron Rayleigh , postulierte 1899 als erster, dass keine kolloiden Teilchen für das Blau des Himmels benötigt werden, dass vielmehr auch reine Luft die entsprechende Streuung, die nach ihm genannte Rayleigh-Streuung , verursacht."Tyndall-Effekt
[11] supported
Mie scattering comes from particles similar in size to light's wavelength, such as water droplets, dust and pollution, and it scatters all visible wavelengths more evenly, producing a whiter, washed-out appearance.
"Mie scattering, by contrast, happens when the particles are similar in size to the wavelength of light, such as water droplets or particles from dust and pollution. These larger particles scatter all visible wavelengths more evenly, creating a whiter, more washed‑out appearance."How Rayleigh Scattering Turns a Blue Sky Into Red/Orange Sunsets Over a Long Atmosphere Path
[12] supported
Near the horizon, Mie scattering and repeated Rayleigh scattering wash the blue out toward white, because the sightline runs through more air and the dusty, humid layers near the ground.
"Looking out at the horizon, that same sightline runs through many times more air and through the dustier, more humid layers near the ground, so Mie scattering and repeated Rayleigh scattering wash the blue out toward white."Sky Horizon Science: Why Is The Sky Lighter At The Horizon?