Why does the sky turn red or orange at sunset on Earth?

In one line

The rule

When the Sun is low in the sky, its light travels through more of the Earth's atmosphere, scattering short wavelengths (blue and violet) and letting longer wavelengths (red and orange) reach our eyes.

Let's understand it simply

Imagine you are watching a cricket match in the evening. As the Sun sets, the sky changes colour. At noon, the Sun is overhead and the sky looks blue. But at sunset, the sky turns red or orange. This happens because sunlight has to travel a longer path through the air. The air acts like a filter, taking away some colours and letting others pass through.

Think of sunlight like a box of crayons with all colours. The air removes the blue crayons first, so only the red and orange ones reach you at sunset.

How it works

1. Sunlight is made of many colours (like a rainbow).
2. When the Sun is overhead, light travels a short distance through the air, and blue light is scattered in all directions, making the sky look blue.
3. At sunset, the Sun is near the horizon, so its light passes through much more air.
4. The air scatters away the blue and green light (short wavelengths).
5. Only the red and orange light (long wavelengths) are left to reach your eyes, making the sky look red or orange.

The story behind it

This effect is called Rayleigh scattering. It was explained by Lord Rayleigh, a British scientist, in the 19th century. He wanted to understand why the sky is blue and why it changes colour at sunrise and sunset. His work helped us understand how light and air interact.

Where you see it in real life

• Sunset at the beach: The sky turns orange and red as the Sun goes down.
• Sunrise in the village: Early morning, the sky glows with red and orange colours.
• During Diwali: Smoke in the air can make sunsets even more colourful, as more particles scatter the light.
• From an airplane: Looking out the window at sunset, you see a band of red and orange near the horizon.
• After rain: Sometimes, the sky is extra bright and colourful at sunset because the air is clean and scatters light differently.

Why it matters

• Helps us understand how light travels and interacts with the atmosphere.
• Used in weather prediction: Colourful sunsets can mean dust or pollution in the air.
• Important for artists and photographers who want to capture beautiful skies.
• Shows how pollution affects the colours we see in the sky.

Common mistakes

• Thinking the Sun itself changes colour: The Sun stays the same, but the air changes what we see.
• Believing the sky is always blue: It changes colour depending on the time of day and air conditions.
• Forgetting that pollution or dust can make sunsets even redder or more orange.

Remember it

At sunset, the sky turns red or orange because the air scatters away blue light, leaving the warm colours for us to see.