Why are sunsets and sunrises red or orange?

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).

Let's understand it simply

Imagine you are playing cricket in the evening. The sun looks big and red, not yellow like at noon. Why? Think of sunlight as a mix of all colors, like a box of crayons. As the sun sets, its light has to pass through more of the air. The air acts like a filter. It scatters (spreads out) the blue and green colors in all directions, so they don't reach your eyes directly. Only the red and orange colors, which are not scattered much, make it to you. That is why the sun and the sky near it look red or orange at sunset and sunrise.

How it works

1. Sunlight enters Earth's atmosphere.
2. During sunset or sunrise, the sun is low on the horizon.
3. The light travels a longer path through the atmosphere.
4. Air molecules scatter short-wavelength light (blue, violet) more than long-wavelength light (red, orange).
5. Most blue and green light is scattered away from your line of sight.
6. The remaining light reaching your eyes is mostly red and orange.

The story behind it

This effect is called Rayleigh scattering, named after Lord Rayleigh, a British scientist. In the late 1800s, he studied why the sky is blue and why sunsets are red. He found that tiny particles in the air scatter short wavelengths of light more than long ones.

Where you see it in real life

• Watching the sun set at the beach: The sky turns orange and red as the sun goes down.
• Early morning in a village: The rising sun looks reddish through the morning mist.
• During Diwali, smoke in the air: Sunsets look even redder because more particles scatter the blue light.
• After rain: The sky can look golden at sunset because clean air scatters less light.
• On a flight: Looking out the plane window, you see a deep red sun at sunrise or sunset.

Why it matters

• Helps us understand how light interacts with the atmosphere.
• Important in weather prediction and climate science.
• Used in photography and art to capture beautiful skies.
• Explains why pollution and dust can change sky colors.

Common mistakes

• Thinking the sun itself changes color: The sun's color does not change, only the light reaching us does.
• Believing sunsets are always red: Sometimes clouds or pollution can make them look pink, purple, or even grey.
• Forgetting that blue light is scattered away, not absorbed.

Remember it

At sunset and sunrise, the sky looks red because the blue light gets scattered away — only red and orange light make it through.