How Does the Sky Color Blue?
The sky’s vibrant blue hue results from scattering of sunlight by Earth’s atmosphere, mostly composed of nitrogen and oxygen molecules smaller than wavelengths of light; they scatter blue light more effectively.
Violet and red wavelengths tend to scatter less, thus leaving blue wavelengths for our eyes.
Rayleigh Scattering
Lord Rayleigh discovered in the 1800s that when sunlight entered the atmosphere it became dispersed more strongly in some directions, creating the blue tint in the sky. This phenomenon occurred because blue light has shorter wavelengths than other colors which caused more scattered by smaller molecules in the atmosphere; red wavelengths on the other hand experience much less dispersal.
But Rayleigh scattering alone cannot explain why the sky is blue – other factors, including atmospheric conditions and presence of dust, pollution, water vapor and other particles can significantly influence intensity and appearance of its blue hue. Seasonal variations also have an effect, as sunlight intensity depends on both pollution levels in the air as well as weather (sunny or cloudy) which all play their part.
As sunlight travels through the atmosphere, it interacts with various gases and particles, the size of which determines its strength of scattering. Gases like nitrogen and oxygen tend to have smaller wavelengths than visible light and thus have an enormous effect on our perception of colour – particularly blue and violet light which tends to scatter more quickly due to shorter wavelengths.
Dust and aerosols also influence the color of the sky. When smaller particles collide with each other they act like ping-pong balls bouncing off each other like pinballs; this results in the creation of haze in the sky that contains particles made from any kind of material that will alter its hue.
Dust in the air will tend to give the sky an amber hue; when there’s too much pollution in the atmosphere, its effects can cause its hue to shift to brownish.
Scientists use radiative transfer and polarized radiative transfer models to gain a better understanding of why the sky is blue, including radiative transfer and polarized radiative transfer models. A major contributor to its color comes from ozone; as levels increase, so too does its contribution towards making the sky appear bluer – but this depends on both surface albedo and observation height.
Atmospheric Refraction
As sunlight travels through Earth’s atmosphere it becomes scattered by gases and particles primarily made up of nitrogen and oxygen, mostly. While light from various wavelengths are scattered, blue wavelengths tend to get scattered more effectively than other colors as you approach red end of spectrum. Denser atmospheres also play a part; those with thicker atmospheres will see bluer skies.
Light passing through our atmosphere is slightly bent as it travels downward, due to its refractive index. This effect is greater nearer the Earth’s surface than at higher altitudes, producing what appears as the apparent horizon when viewing distant mountains or airplanes, and producing the Green Flash seen when planets rise over our horizon.
The color of the sky changes with time of day and pollution levels in the air, being lighter if air quality is clear, while darker skies indicate polluted conditions. Seasonally too, its hue may change – lighter in spring/summer months but darker towards fall/winter.
Ozone and atmospheric dust do not significantly contribute to the blue hue of the sky; Rayleigh scattering is responsible. Open water surfaces also reflect sunlight at wavelengths which contribute to this hue, while seas and oceans absorb long wavelengths which would otherwise cause them to look reddish-orange in hue.
Rayleigh scattering and atmospheric refraction account for most of the blueness in the sky, though there is some contribution from ozone absorption at both extremes of altitude: nearer the zenith at higher altitudes than lower ones; this effect decreases with increasing stratospheric aerosol concentrations.
Dust and Aerosols
The color of the sky depends on a combination of factors, including sunlight and aerosol particles in the air (known as aerosols). Particle sizes determine how much light they scatter while their density has an impactful impact on how bright the air appears – for instance dense smog and smoke can cast murky gray hues across the skies while decreasing how much blue light gets scattered back out, making the sky appear less bright overall.
Nature produces vast swaths of aerosols across both water and land, as sandstorms disperse fine mineral dust particles into the atmosphere, while wind-driven spray from ocean waves carries sea salt skyward. Around 90 percent of global aerosol production comes from nature while humans create the rest; large areas in both America and Europe are particularly prolific sources for industrial-type aerosols such as sulfates from power plants, black carbon from car exhaust fumes and organic/particulate matter emissions from power plants/car exhaust/organic/particulate matter/organic matter/etc.
Aerosol particles may be small, but their reach can be astoundingly far. A cloud that forms over the Sahara could ultimately reach the Caribbean; winds could then carry these particles throughout Asia to Japan and the central Pacific Ocean – and in extreme cases even to the Arctic Ice Cap!
Aerosol types also make an impactful statement about how we perceive climate change and environmental pollution: black carbon from soot can prevent precipitation by warming the surrounding atmosphere, while creating a haze that turns clouds bluish-gray and blocks solar radiation before reaching Earth.
An additional factor is ozone levels in the air. Ozone reacts strongly with blue and violet light wavelengths, so more of it makes the sky appear bluer – most notably near its zenith.
Seasons
The blue color of the sky changes throughout the year. In summer it tends to become lighter and brighter; by fall it has deepened significantly due to atmospheric differences. Cooler air contains less water vapor, reducing its ability to disperse light evenly as it scattered by droplets or haze; large droplets become less prominent, too; moreover as sun lowers further in sky during fall, shorter wavelengths like blue are able to travel further without becoming easily scattered by droplets and haze causing milky skies!
After rain showers or during cooler temperatures in fall, we often notice an intensified blue in the sky. It also becomes evident when gazing upon the night sky during a cold front or winter season – this time because reduced cloud cover and increased moisture levels in the atmosphere result in bluer skies than normal.
Sky blue conjures feelings of calmness and tranquility, reminding us of clear seas and open skies. This positive and optimistic hue inspires trust between people. Sky blue works especially well when used in nature photography to evoke vastness and space.
Since sky blue is such a light and muted shade with minimal saturation or contrast, it works beautifully when combined with other light hues. Coral (#ED80E9) adds vibrancy and energy while emerald green accentuates its jewel tone; gunmetal (#FF1D8D) softens the intensity with its rich earthy textures.
As with any color choice, choosing blues that suit the season and subseason you live in is of utmost importance. With Rise Styling Color Kit’s personalized skin toning functionality, identifying your ideal shades of blue has never been simpler!