Why does sunset look different from sunrise

Curiosities: What determines the colors of the sky at sunrise and sunset? November 6, Photo: Jeff Miller. Share via Facebook. With this larger distance of atmosphere to cover, the blue light gets tired. But the red, orange and yellow light have longer wavelengths. This means they can scatter for longer and travel through the atmosphere to reach us. Portsmouth Climate Festival — Portsmouth, Portsmouth. Edition: Available editions United Kingdom.

Become an author Sign up as a reader Sign in. Light from our setting sun reflecting off storm clouds can give off a some vivid shades of pinks, purples and oranges.

The sun is perched on the horizon. Can you tell whether it's rising or setting? Contemplating this scenario while gazing sunward at dusk or dawn, we might feel as if we could sense the difference between the two times of day.

But in real life, it's impossible to completely divorce our perceptions of the scene from our awareness of the hour. So, is there any objective way to distinguish an upward-trending sun from a downward one? According to atmospheric physicists David Lynch and William Livingston, the answer is "yes, and no.

Molecules send the light waves off in different directions. We call this process scattering. Sunlight scatters many times before reaching our eyes. Blue light travels fast, so it scatters more often than most other colors. That's why we don't see the bright colors of the sunset during the day! So much blue light is scattered that it hides most other colors. Other colors peek through at sunrise and sunset because the light travels farther to reach us. That allows the other colors of light waves to scatter more often.

Would you believe the sky could actually be purple? Purple waves move faster than blue ones, so more purple light is scattered through the sky. Then why is the sky blue?

The sensitivity of our eyes influences the colors we see. Human eyesight peaks in the middle of the rainbow. Because blue is closer to the center than purple, we see a blue sky instead of a purple one. If you've seen more than one sunset, you know they're not always the same.

Why is that? Many people say the most beautiful sunrises and sunsets occur in autumn and winter when the atmosphere is dry and allows light waves to travel more quickly.

However, many events affect sunsets by adding new gas molecules to the air. For example, volcanic eruptions send debris into the atmosphere. These particles cause light waves to scatter at a higher rate. Anyone who sees a sunset just after an eruption will see a glowing orange sky. Pollution also changes the sunrise or sunset. In crowded cities, pollution from auto engines blocks many shades of light.

The sunsets in highly polluted areas are just bright red instead of a pattern of colors. Finally, clouds influence the appearance of a sunrise or sunset. You might worry that clouds would cover the event from view. However, a few clouds in the sky make the sunrise or sunset look even more breathtaking. Clouds catch the colorful rays as the sun rises or sets, resulting in colors rising higher into the sky. Have you ever watched the sunrise over the ocean on a cloudy morning?