By: A. Cordeiro
The sky changes colour so regularly that sometimes, we even forget how fascinating the sunset and sunrise can be. But have you ever stopped to wonder why the sky changes color, or how the sky can become a beautiful range of eye-catching colours?
Well, the sky changes colours due to a phenomenon called the scattering phenomenon. This theory was developed by a man named Gustav Mie in 1908. The blue sky you see during the day, the dark nights, and the spectrum of colours you see at sunset and sunrise are all due to this phenomenon.
As well known, the atmosphere which surrounds the Earth, is made up of an abundant number of molecules and small particles. The rays of light that reach the Earth from the Sun go through these molecules and particles, which causes the direction of these rays of light to change and consequently scatter. The manner in which the rays of light scatter is what determines the light that comes from the sky. However, what determines the colour of the sky is the wavelength and the size of the particle the light reaches.
The blue colour that we see in the sky during the day is a result of the short-wavelength blue and violet that are scattered by the particles and molecules in the atmosphere. During the day, these colours reach our eyes more than the other colours in the rays of Sun. This blue and violet light comes from all directions and reaches our eyes on days which are moderately clear. Humans cannot see the colour violet as well as other colours, which is why we see the sky mostly blue and not violet.
During the sunset and sunrise, the rays of sun reach more particles than during the days as the Sun is lower on the horizon rather than higher away in the sky. This means that there is more atmosphere for the light to reach and more particles are able to scatter that blue and violet light away from your eyes. The other colours that reach the atmosphere of the Earth through the light rays still travel towards your eyes, which is why you see yellow, orange, and red during the sunset and sunrise. Red is the colour with the longest wavelength out of all of the visible light colours. And, as the Sun is red once it reaches the horizon, the red light’s wavelength occludes all the other colours in the light.
The night is dark as the light derived from the Sun does not reach that specific area of the Earth, meaning you can only see other points of light, such as the moon, stars, and other planets.