How Sunsets Work
At one time or another, all of us have stopped to stare at a beautiful sunset with its red and orange colors. You can take in a colorful sunset anywhere you go, but some parts of the world, like deserts and tropics, are well known for their splashy palette of colors. Why is it that the sky looks like it's bleeding when the sun goes down? And why are some parts of the world more colorful than others?
The Colors of the Sun
As the sun sets, the light must travel through more of the atmosphere before the rays get to you. By more atmosphere, that means more molecules which scatter the blue and violet light. (Think of it like a glass of water - at mid-day, the light is refracting through the center of the glass of water. With a sunset, the sun is refracting across the surface of the glass of water). If the path is long enough, the blue and violet lights go further than our eye can see. This leaves the pink, orange and red colors for us to look at. So that's why sunsets are usually pink, orange and red.
Sunsets and Pollution
The most beautiful sunsets happen when the air has small particles of dust or water, like after a volcanic eruption. These particles reflect light in all directions, resulting in more reds and yellows, and less pinks. The more particles in the air, the more the light is scattered. Cities with high pollution have great sunsets cuz more light bounces around. If the air is very dry and clean, like in the Arctic, the sky near the horizon will stay blue and the sun will be bright orange.
Have you heard something about green flashes? Just because you've never seen one doesn't mean they aren't real. They really do happen! A green flash can be seen when part of the sun suddenly changes color (at sunset and sunrise). The green doesn't flash - it just means the color is sudden and brief (about a second or two). If you're running out to watch the next sunset for a glimpse of green, there are a few things to consider. Location is really important, you'll need help to see it (binoculars, magnifying glass, etc. will do) and really clean air is crucial. Remember - you shouldn't stare directly at the sun, unless it's almost below the horizon.