Sunsets occur in relation to the viewer when the turning of the earth causes the horizon to pass up and over the sun's position in the sky. When this happens, atmospheric conditions and different types of clouds can produce a wide variety of sunset effects, ranging from the mundane to the spectacular.
Perfectly clear conditions tend to produce somewhat less interesting sunsets. Because the drama of a sunset is usually created by the interaction of light with cloud patterns, a sunset on a clear day creates fewer effects. Clear sunsets can still be beautiful, particularly if they occur over an appealing landscape, but they tend not to be the most memorable of sunset events. The exception to the mundane nature of cloudless sunsets is when the viewer is treated to a "green flash" -- an atmospheric phenomenon caused by the refraction of light that produces a green light in the sky just after the sun has set.
The most dramatic sunsets occur when the sky is overcast with a thick layer of clouds but with a clear strip of sky on the western horizon. When these conditions prevail, the sun appears to drop down out of the clouds and then illuminates the underside of the clouds as it drops down to the horizon. Under the right atmospheric conditions, this can produce gorgeous light effects involving intense tones of orange, yellow and red.
Sunsets are primarily created by the kinds of clouds that are prevalent at the time the sun sets. In addition to the previously mentioned full-sky cloud cover, interesting sunsets can also be created by high, puffy cumulus clouds and by misty or smeary clouds on the horizon that partially obscure the sun as it sets. The only clouds that don't make an interesting sunset are thick, dark clouds that cover the western horizon, a condition that obscures the sun altogether and removes any possibility of a visible sunset.
The "God Ray" is the star of the sunset repertoire. This phenomenon occurs when the sun is behind a bank of clouds that is thick enough to obscure most of the sunlight but still has some holes in it. Under these conditions, isolated shafts of sunlight will shoot through the cloud, creating "God Rays," so named because they resemble any number of inspiring photographs used on church calendars and inspirational posters. "God Rays" can occur independently of a sunset, but are most impressive when they happen toward the end of the day as the sun approaches the horizon.
- Photo Credit Thomas Northcut/Photodisc/Getty Images