What Causes the Sky to Change Colors When the Sun Rises and Sets?
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The Sun and Sky
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The color of the sky is directly related to the position of the sun and the interaction (or scattering) between elements in the Earth's atmosphere and the different wavelengths of light emitted from the sun. To the naked eye, sunlight appears as white but, actually, all sunlight emits several different wavelengths of color, from violet to red, known as the ultraviolet spectrum. In the ultraviolet spectrum, violet, blue and green light have the shortest wavelengths, while yellow, orange and red have the longest.
To understand what causes color when the sun rises and sets, it's important to first understand what makes the sky blue.
Blue Skies
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A blue sky is caused by a process called Rayleigh scattering. When the sun is positioned high in the sky, it emits light at a relatively short angle. This shorter angle allows the longer red, orange and yellow wavelengths to pass through the atmosphere, unhindered. But the shorter blue and violet wavelengths get absorbed by gasses in the atmosphere, which scatters their light, causing the sky to register as blue to the human eye.
Water vapor and pollution also affect the color of the sky. A high amount of water vapor, as on a cloudy day, deflects the light and causes the sky to appear gray. -
Sunrise
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During a sunrise, the sun is lower in the sky, which lengthens the angle at which light reaches the Earth. As a result, the shorter violet, blue and green light never reaches the eye, so only the yellow, orange and red light is visible. Because red has the longest wavelength, the first light of dawn often appears pink or red--depending on the particles in the atmosphere. As the sun moves further up the sky, the reds and yellows fade as the scattered blue light becomes more visible.
Sunset
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A sunset is similar to a sunrise, only in reverse. However, one major difference between the two is that a sunset tends to be more brilliant and colorful. The main reason for the more brilliant sunset is that most humans and animals are active during the day and kicking dust and debris into the atmosphere. This dust and debris filter the light wavelengths creating brilliant colors--similar to placing colored gels in front of a stage light. Urban and industrial areas tend to have the most brilliant sunsets because of the amount of pollution in the atmosphere.
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Sunrise During a sunrise, the sun is lower in the sky, which lengthens the angle at which light reaches the Earth. As a result, the shorter violet, blue and green light never reaches the eye, so only the yellow, orange and red light is visible. Because red has the longest wavelength, the first light of dawn often appears pink or red--depending on the particles in the atmosphere. As the sun moves further up the sky, the reds and yellows fade as the scattered blue light becomes more visible. Sunset A sunset is similar to a sunrise, only in reverse. However, one major difference between the two is that a sunset tends to be more brilliant and colorful. The main reason for the more brilliant sunset is that most humans and animals are active during the day and kicking dust and debris into the atmosphere. This dust and debris filter the light wavelengths creating brilliant colors--similar to placing colored gels in front of a stage light. Urban and industrial areas tend to have the most brilliant sunsets because of the amount of pollution in the atmosphere. Read more: What Causes the Sky to Change Colors When the Sun Rises and Sets? | eHow.com http://www.ehow.com/how-does_4897152_change-colors-sun-rises-sets.html#ixzz1WHUQXl2p.
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Blue Skies A blue sky is caused by a process called Rayleigh scattering. When the sun is positioned high in the sky, it emits light at a relatively short angle. This shorter angle allows the longer red, orange and yellow wavelengths to pass through the atmosphere, unhindered. But the shorter blue and violet wavelengths get absorbed by gasses in the atmosphere, which scatters their light, causing the sky to register as blue to the human eye. Water vapor and pollution also affect the color of the sky. A high amount of water vapor, as on a cloudy day, deflects the light and causes the sky to appear gray. Read more: What Causes the Sky to Change Colors When the Sun Rises and Sets? | eHow.com http://www.ehow.com/how-does_4897152_change-colors-sun-rises-sets.html#ixzz1WHU7pEjD.
