Why is the sky red or orange at sunrise and sunset?

In one line

The rule

When sunlight passes through the atmosphere, shorter wavelengths (blue and violet) are scattered more than longer wavelengths (red and orange). At sunrise and sunset, the sun’s light travels a longer path through the air, so most of the blue light is scattered out, leaving mainly red and orange colors.

Let's understand it simply

Imagine you are playing cricket in the evening. As the sun goes down, its light looks more orange or red. This happens because sunlight has to travel through more of the air near the ground. The air acts like a filter. It removes some colors from the sunlight before it reaches you. The blue light gets scattered in all directions, so you mostly see the red and orange colors that are left.

How it works

1. Sunlight is made of many colors mixed together (like in a rainbow).
2. When the sun is high in the sky, its light travels a short path through the air, so blue light gets scattered and the sky looks blue.
3. At sunrise and sunset, the sun is near the horizon, so its light travels a much longer path through the air.
4. The air and dust scatter the blue and green light away from your line of sight.
5. Only the red, orange, and yellow light (which scatter less) reach your eyes, making the sky look red or orange.

The story behind it

The explanation for this effect comes from the study of light and its behavior in the atmosphere. Lord Rayleigh, a British scientist in the 19th century, explained why the sky is blue and why it changes color at sunrise and sunset. He showed that short wavelengths of light (like blue) scatter more than long wavelengths (like red).

Where you see it in real life

• Watching the sun rise over a river or mountain: the sky looks orange or red.
• During Diwali, smoke in the air can make sunsets look even redder.
• On a dusty road in summer, sunsets appear more orange because dust scatters more blue light.
• After heavy rain, the sky at sunset can look very clear and bright red.
• In cities with air pollution, sunsets are often deep orange or red.

Why it matters

• Helps us understand how light and the atmosphere work together.
• Used in weather prediction: very red sunsets can mean dust or pollution in the air.
• Important in art and photography for capturing beautiful scenes.
• Shows how pollution and dust affect what we see in the sky.

Common mistakes

• Thinking the sun itself changes color: It’s the air that changes what we see, not the sun.
• Believing the sky is always blue: It depends on the time of day and the path of sunlight.
• Forgetting that dust and pollution can make the effect stronger.

Remember it

At sunrise and sunset, sunlight travels through more air, so blue light scatters away and red/orange light stays — that’s why the sky looks red or orange.