Rayleigh scattering is responsible for the sky’s blue color. This scattering is the scattering of electromagnetic energy (of which light is one type) by particles with a significantly shorter wavelength.

Blue light is spread above other colors in the spectrum, making it more visible. Thereby making the sky appear blue to the human eye.

We must first understand light to understand why the sky is blue. Sunlight looks to be white, but it is actually made up of a rainbow’s worth of colors.

Light is a wave of energy, and various colors have varying wavelengths. Red light, which has the longest wavelength, is at one side of the spectrum, while blue and violet light, which has a much shorter wavelength, is at the other.

 What Causes the Sky to Be Blue?

The small molecules of gas (mainly nitrogen and oxygen) in the air disperse or deflect the Sun’s radiation as it enters the Earth’s atmosphere.

As these molecules are far smaller than apparent light wavelengths, the quantity of scattering is proportional to the wavelength. Rayleigh scattering is the name given to this phenomenon after Lord Rayleigh, who was the first to discover it.

Since shorter wavelengths (violet and blue) scatter more forcefully than other colors, more blue light is reflected towards human eyes.

You might be wondering why the sky does not really appear purple, given that violet light scatters far more than blue light. This is due to the fact that sunlight contains less violet and our eyes are more reactive to blue.

The blue light which brings the sky its tint is intense enough to make all of the stars you view at night vanish since their light is considerably weaker.

During sunset and sunrise, the angle during which the sun’s rays reach the atmosphere varies considerably. And the bluest and greenish (shortened) wavelengths of light are dispersed well before hitting the lower atmosphere, leading to a sky with more orange and red colors.

What Causes the Blue to Drift Away as It Approaches the Horizon?

You’ll also observe that the sky is the brightest overhead and fades to a faint color as it approaches the horizon. This is due to the fact that illumination from the horizon has to travel farther through the air, scattering, and rescattering.

This light is also scattered and reflected by the Earth’s surface. The supremacy of blue light is reduced as a consequence of the increased dispersion, and you see more white light.

Why Ocean Water Appears Blue?

The absorbance of red light by water gives it a blue appearance. When light collides with water, part of the photons are absorbed by the molecules of water. Everything absorbs light at a distinct wavelength (the green t-shirt absorbs red) and reflects the residual colors back to the viewer (this is why the t-shirt seems green).

Because there isn’t adequate water to absorb sufficient photons in shallow bodies of water (such as a drinking glass), light penetrates fully, leaving the water colorless.

As there are several water molecules in the path of the photons in deeper depths, not all light wavelengths can entirely penetrate the liquid.

What Causes the Sunset to Be Red or Orange?

The Sun is quite low in the sky during sunrise and sunset, this implies that the light you see has traveled through a significantly thicker layer of the atmosphere.

Since blue light is dispersed more severely by the environment, it is scattered numerous times and redirected in different directions before reaching mankind. This indicates that there is still a lot of yellow and red light for us to view.

Light travels through less atmosphere around midday. When the sun hits the Planet’s surface, it is dispersed in all directions, giving us blue light. Since blue flows in shorter, smaller waves, it is dispersed more than most other colors. Light has to travel further through the atmosphere at sundown, though.

You notice the longer wavelength of yellow and red light because the lower wavelengths of blue light are scattered further as sunlight travels over large distances.

As It Rains, Why Do the Clouds Turn Grey?

Clouds appear grey due to their thickness, or height. Clouds are composed up of small water or ice particles. Condensation of water vapor within pockets of rising air to generate them. The air is elevated under the appropriate conditions, enabling the cloud to rise up and up.

Clouds’ minute water droplets and ice crystals are the perfect sizes to disperse all colors of light, unlike the smaller air molecules that disperse blue light most efficiently. When all hues are present in light, you see it as white.

Whenever clouds are thin, they allow a lot of light to pass through, giving them a white appearance. However, as with any light-transmitting object, the thicker it is, the less light it transmits. The bases of clouds become darker as the thickness develops, although they continue to spread all colors. This appears grey to all of us.

Clouds’ fairly flat bottoms have always been a little grayer than their sides if you look closely. The grayer the bottoms of the clouds appear as they get up.

Why Does It Look Like Clouds Always Gather in Clumps?

The earth’s atmosphere, particularly localized areas of it, is not thermally balanced. The sun rises and sets, and surface temperatures rise and fall.

Simply said, there isn’t enough time for the effects of such massive thermal disturbances to dissipate uniformly. The sum of all disturbances (such as temperature variations and ocean waves) adds to the volatility you see across short distances.

The majority of clouds form as air rises. An amount, or package, of air, expands and cools as it rises. In addition, the ascending air’s humidity levels rise. Condensation of water vapor produces small droplets of water or ice crystals when the parcel approaches saturation, forming a cloud.

Saturation happens at a specific height, that differs depending on the atmosphere’s temperature and moisture composition. Clouds do not develop underneath this condensing level, which explains why cloud bottoms have a distinctive appearance and are usually flat. The borders of certain clouds are more diffuse than others.

Bottom Line

Rayleigh scattering is a key factor in many of the color visions we perceive in space. Have you ever wished for a different color in the sky or at sunset?