The short waves of blue light disperse more than other colours in the spectrum, giving the hue blue more visibility and giving the sky its blue appearance to the human eye.
We must first gain a basic understanding of light in order to comprehend why the sky appears blue. Although sunlight appears white, it actually consists of a spectrum of various hues, as can be seen when they are dispersed in a rainbow.
The wavelength of each hue in the spectrum of light can be thought of as an energy wave. Red light, which has the largest wavelength, is at one end of the spectrum, and blue and violet light, which has a much shorter wavelength, are at the other.
How come the sky is blue?
The microscopic gas molecules in the air, primarily nitrogen and oxygen, scatter or deflect the Sun’s light as it enters the Earth’s atmosphere. The quantity of scattering is dependent on the wavelength because these molecules are much smaller than the wavelength of visible light. Rayleigh scattering is the name of this phenomenon, which was initially identified by Lord Rayleigh.
The strongest scattering occurs at shorter wavelengths (violet and blue), hence more blue light is dispersed in our direction than any other hue. Given that violet light is much more strongly scattered than blue light, you might be wondering why the sky doesn’t actually appear purple. This is because our eyes are considerably more sensitive to blue and sunlight doesn’t include as much violet to begin with.
The blue light that gives the sky its colour is so strong that it completely obscures all of the stars we see at night since the light they produce is considerably fainter.
Why is the blue fading as it approaches the horizon?
Additionally, you may have noticed that the sky is typically at its most vivid overhead and becomes paler as it approaches the horizon. This is because the light from the horizon has spread and rescattered as a result of having to travel farther through the air. This light is also scattered and reflected by the surface of the Earth. This increased scattering causes the dominance of blue light to decrease, which causes us to see more white light.. The dominance of blue light is reduced as a result of this enhanced scattering, which causes us to see more white light.
