Whether a nature lover or not, the ever changing sky colour will still catch your fancy. While gazing at the wide blue blanket that engulfs our planet, you would have probably wondered, “Why is the sky blue and how does it change colour?” Or if you saw a beautiful sunset or sunrise, you would have thought, “How is it so beautiful in vivid colours of pink and red?”

We all know that the sky is blue and it does transition to a deeper blue or almost black at night and reflects a pleasant light blue in the morning. The question is that when the rainbow is made up of seven colours and out of all the colours we see in nature, what makes the sky - blue?

Without much ado, we will tell you the magical scientific mystery behind this phenomena.

Why is the sky always blue?

The white light coming from the Sun is made up of all the colours of the rainbow. We see all those colours when we look at a rainbow. Raindrops act as tiny prisms when lit by the Sun, bending light and separating it into its different colours. Scattering affects the colour of this light coming from the sky, but the details are determined by the wavelength of the light and the size of the particles.

Courtesy - Travel.Earth

The short-wavelength blue and violet are scattered by molecules in the air much more than other colors of the spectrum. This is why blue and violet light reaches our eyes from all directions on a clear day. But because we can’t see violet very well, the sky appears blue.

And because red has the longest wavelength of any visible light, the sun is red when it’s on the horizon, where its extremely long path through the atmosphere blocks all other colors.

How does the sky change colours on certain days and at certain times?

When the light comes from the sun, the light waves of different lengths travel through the atmosphere. These light waves come into contact with particles in the earth’s atmosphere- like dust, ice crystals, water droplets. The light waves then bounce off these particles and get scattered here and there in the atmosphere.

What determines Sky’s colors at Sunrise and Sunset?

Particles that are small in size as compared to the light waves scatter blue light. Red light waves are scattered by gas molecules of nitrogen and oxygen in our atmosphere. Thus we see the blue sky most of the time. But when the light waves have to travel a great distance, the blue light is removed. So during sunrise and sunset, when the sunlight travels a really long path to reach us the blue light is removed leaving mostly orange, yellow, and red lights. This light is reflected by clouds and other objects and makes the sky a beautiful, colourful reddish, orange one!

Thus the colour of the light we see depends on the size of the particle directly proportional to the wavelength of the light.

Isn’t our planet gifted with wondrous mysteries that always leaves us wondering - ‘Why’ and ‘How’ does this happen? We understand how curious your minds are! To fuel this curiosity, we will again be back with another round of our, 'Curious Minds: Why & How" series.

At Practically, we have focused on simplifying the most complex scientific concepts for you. If you are someone who believes in #LearningPractically then go and check out our immersive learning app that offers 3D videos, simulations, and AR experiences! Also, try out our revolutionary Scan Anything feature which helps you to learn from textual images and daily objects around you.

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