“Gases and particles in Earth's atmosphere scatter sunlight in all directions. Blue light is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.”

Sunlight reaches Earth's atmosphere and is scattered in all directions by all the gases and particles in the air. Blue light is scattered more than the other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.

“Rayleigh scattering refers to the scattering of light by small gas molecules, with **shorter wavelengths (blue light) being scattered more effectively** than longer wavelengths (red light). This answers the popular question of ‘**why is the sky blue?**’ … So a consequence is that if the sun is out and high in the sky the **blue light is getting scattered more and when we look at the sky we see the diffuse blue light from the Rayleigh scattering of the sunlight**.”

The blue color of the sky is caused by the scattering of sunlight off the molecules of the atmosphere. This scattering, called Rayleigh scattering, is more effective at short wavelengths (the blue end of the visible spectrum). Therefore the light scattered down to the earth at a large angle with respect to the direction of the sun's light is predominantly in the blue end of the spectrum.

“In fact, it’s the Earth’s atmosphere, and a process known as 'scattering', that causes our skies to be blue. As white light passes through our atmosphere, tiny air molecules cause it to ‘scatter’. The scattering caused by these tiny air molecules (known as Rayleigh scattering) increases as the wavelength of light decreases… Therefore, blue light is scattered more than red light and the sky appears blue during the day.”

A clear cloudless day-time sky is blue because molecules in the air scatter blue light from the Sun more than they scatter red light. He [Lord Rayleigh] showed that the amount of light scattered is inversely proportional to the fourth power of wavelength for sufficiently small particles. It follows that blue light is scattered more than red light by a factor of about 10, and this scattered blue light is what we see when we look away from the Sun.

The sky is blue because molecules in the atmosphere scatter shorter wavelength light, such as blue and violet, more effectively than longer wavelengths such as red. Although violet light is scattered even more strongly, the human eye is less sensitive to violet, and some violet is absorbed higher in the atmosphere; therefore, the sky appears predominantly blue to us.

“Rayleigh scattering is a phenomenon that describes how light is scattered by small molecules in the atmosphere… This scattering effect is primarily responsible for the blue color of the sky, as shorter wavelengths of light, such as blue and violet, are scattered more efficiently than longer wavelengths like red. Despite violet light being scattered even more, the human eye is more sensitive to blue light, which is why the sky appears blue rather than violet.”

“Sunlight is made up of all the colours of the rainbow. As it passes through the atmosphere, it interacts with molecules and tiny particles of air. **Rayleigh scattering causes shorter wavelengths of light (blues and violets) to be scattered more efficiently than longer wavelengths (reds and yellows).** Our eyes are more sensitive to blue light and the Sun emits relatively less violet light, so the **scattered light that we see when we look at the sky appears predominantly blue.**”

“Sunlight is made up of many different colours of light. As it passes through the atmosphere, it is scattered by molecules of air. **Rayleigh scattering is much more efficient at scattering short-wavelength light, such as blue, than long-wavelength light, such as red.** This scattered blue light reaches our eyes from all directions, which is **why the sky looks blue most of the time.** If Earth had no atmosphere, the sky would look black even in daytime.”

“The blue color of the sky is due to Rayleigh scattering. As sunlight passes through the atmosphere, the gas molecules scatter the shorter wavelengths (blue and violet) more strongly than the longer wavelengths (red). Because our eyes are more sensitive to blue light and some violet is absorbed by the upper atmosphere, we perceive the sky as blue.”

The video explains: “The blue sky is caused by something called **Rayleigh scattering**. … When direct light from the Sun enters the atmosphere, it begins to scatter around. However, this scattering is **color dependent**. Higher frequency visible light, that means light near the **blue end of the visible spectrum, is scattered almost ten times as much as light near the red end of the spectrum.** … Also, technically, the sky isn’t blue. It’s **bluish white**. While blue is being scattered more, all the colors are being scattered a little bit. All the colors together make white, but white dominated by blue is bluish white. … So why is the sky blue? It’s blue because of Rayleigh scattering in the upper atmosphere.”

Although Rayleigh scattering favors even shorter violet wavelengths, the solar spectrum has less violet light than blue and the human eye’s cone cells are less sensitive to violet than to blue. Combined with some absorption of violet light in the upper atmosphere (by ozone and other gases), this means the scattered light that reaches observers is perceived predominantly as blue rather than violet.

In this video, we explain Rayleigh scattering in simple words — from why shorter wavelengths (blue and violet) scatter more than longer wavelengths (red and orange), to why the sky turns red at sunset, why it's blue and not violet. A lot of blue light is scattered around in the sky during the day, giving the sky its blue hue, while our eyes are more responsive to blue than to violet and some violet is absorbed in the atmosphere.