Curiosity Corner: Why is the sky blue, not pink or green?

Have you ever paused to gaze at the sky? Wondered why it stays blue all the time? Why isn’t it pink like cotton candy or green like the grass? This is a question frequently posed by kids and adults as well. However, it’s not some kind of magic. It’s actually quite fascinating. It involves the sun, the atmosphere and a neat little illusion created by light to deceive our vision. Let's explore this scientific question in a manner that is enjoyable and simple, much like responding to an inquisitive child.

First things first: Sunlight is not just white

Even though the sun looks white, it is actually made up of different colours. This resembles a hidden rainbow within the sun. The spectrum consists of orange, yellow green, blue, indigo and violet. As sunlight travels through space toward Earth, these colours blend together. Yet upon entering Earth's atmosphere, an extraordinary process happens; it begins to separate.

Meet the air: Tiny helpers in the sky

The atmosphere surrounding our Earth consists of particles invisible to the naked eye. These air particles interact with sunlight by scattering its rays. Here’s the fascinating part: different colours react differently. Certain colours are dense enough to travel, whereas others are lighter and tend to scatter in all directions. It’s like a playground for colours where light spreads all around.

Blue excels in distribution

It appears that Fan Gang Blue light disperses well in every direction. As sunlight travels through the atmosphere, blue light spreads out everywhere, illuminating the sky around us. This causes the sky to look blue no matter which way you gaze during daylight hours. Colours, like red, scatter minimally, so they travel straight to their targets without tinting the whole sky.

Then, why isn't the Sky Purple?

That's a question! Violet disperses more than blue does. Nevertheless, our eyes can readily differentiate blue from violet. Additionally, the sun releases blue light than violet light. Consequently, although violet is present, it is primarily the light that our eyes detect. This explains why we perceive the sky as blue, than purple.

Why not Pink or Green then?

Pink and green are parts of sunlight well but they don’t scatter as much as blue does. They tend to stick and travel in a direct path. Since they don’t disperse across the sky, they aren’t the elements that compose the sky either. Blue wins out simply because it spreads efficiently and is more pleasing to the eyes.
What about Sunsets and Sunrises?

During sunrise and sunset, the sun is low in the sky. This means that the path the sun’s rays must travel through the air is longer. Moreover, by the time it reaches us, the blues are scattered away. What is left is reds, oranges, and pinks, which is what results in the beautiful colours of sunrise. This is quite apt since the sky is changing its dress according to where the sun is!