The sky palette has many colours to offer like blue, white and grey, yellow, red and orange alternate, and if you add the rainbows, the joy of colour seems limitless. But why Why Is Sky Blue on a beautiful day and red to orange-red at sunrise or sunset and has no colour at night?
The cloudless sky is dominated by blue colour during the day, although behind it is the blackness of the universe. On beautiful evenings the sky turns a breathtaking red, even though the sun shines in the same colour as during the day. The secret behind this variety of colours lies in the way the sunlight scatters in the atmosphere. The fact that the sky is black at night and you can easily see the stars and the moon suggests that the colour of the sky is related to the light of the sun. How exactly the blue sky or the dawn appears in the atmosphere is somewhat more complicated.
Diffused light
The sun’s light appears yellowish-white to us, but it’s made up of all the colours of the rainbow or VIBGYOR(violet, indigo, blue, green, yellow, orange and red). Each of these colours corresponds to electromagnetic radiation of a certain wavelength. This wavelength is the shortest for blue and the longest for red.
The different wavelengths now play an important role when the light collides with gas molecules on its way through the atmosphere and changes its direction. The light is scattered as it enters the atmosphere. Whenever we do not look directly at the sun, we only see scattered light that comes into our eyes through a few detours from the sun. Therefore it is the scattered light that determines the colour of the sky.
To put it simply, the light consists of several light beams bundled together that move like a wave. When you see all the rays of light at once, it appears as white. However, if the light is refracted by a prism or a raindrop or the atmospheric gases, the light beam splits into its spectral colours, like in the rainbow, that make up the white light. All these colours have a different wavelength, which is the distance between two successive wave crests. The blue light has a very short wavelength, and red light has a very long wavelength.
Why is the sky blue?
Now, the answer to the question why is the sky blue during the day is that when the sun is higher or above us in the sky, the sunlight has to cover a short distance through the atmosphere to reach Earth’s surface. The blue light is very strongly scattered in the atmosphere by water and gas molecules and thrown back. Due to the scatter, the blue component is reduced so much that the red reaches the surface and blue is mostly scattered in the sky. That is why a cloudless sky appears blue to us during the day.
Why is the sky red in the evening and the morning?
The red colour of the sky in the evening or morning is because the sun is low in the sky. Sunlight has a longer distance to cover through the atmosphere due to its angle. The gas or water molecules quickly intercept the short-wave blue light in the atmosphere and only the long-wave red light reaches the viewer.
Why is the sky grey and cloudy?
In addition to the clear sky blue or sky red, grey is another colour that is often observed in the sky. The grey sky is created by larger dust and water particles in the atmosphere, which does not split the sunlight, but reflects it directly. The result is a greyish-white sky.
Why is the colour of the sky different on other planets?
It can be explained by a phenomenon called Rayleigh scattering. Rayleigh scattering states that the lower the wavelength of radiation, the more it is scattered. Rayleigh scattering is valid in the entire universe. The reason why other planets have a different colour of the sky is due to the density and the composition of the respective atmosphere. The Earth’s atmosphere consists largely of nitrogen and oxygen. The planet Mars, on the other hand, is very thin and contains large amounts of carbon dioxide and small iron oxide particles. Venus also owns large amounts of carbon dioxide, but a very dense atmosphere. In both cases, the short-wave blue light rays have no chance of reaching the planet surface, and only the red light rays make it to the surface, making the sky of these two planets appear reddish.
Now you not only know why is sky blue but also why the skies of any planet appear in a particular colour. But do you know what is the colour of the sun?