Fading AwayLucas MalheirosAward: Top 100
School: minnetonka high school The black coloring of this old parking lot street sign, like many other painted objects, has slowly faded away due to its exposure to the sun; the molecules that give the object its color are being broken or altered down by ultraviolet rays. While humans can only see the visible light emitted from the sun, it also emits ultraviolet light. Visible light, ultraviolet rays, and all other forms of electromagnetic radiation are emitted as photons, which are discrete energy packets. The photons emitted as ultraviolet light from the sun have a great amount of energy. When some of these ultraviolet photons pass through Earth's upper atmosphere and make contact with colored molecules, such as the black paint on a street sign, the photons are powerful enough to trigger small chemical reactions that alter their color. This process is known as photodegradation, where ultraviolet radiation breaks down or alters the molecules that determine color, called chromophores. There are several processes by which chromophores can be broken down or altered by the sun's ultraviolet rays. The bonds of the molecule may be directly split by a photon, causing the paint color to fade. Or, the chromophore may undergo oxidation instead. When it reacts with oxygen, the molecule may no longer function as a chromophore, also fading color. And so, every time the sun shines, this street sign will continue to fall victim to the slow but destructive process of photodegradation, its colors fading to pale white as its chromophores are shattered. 
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