Sunday, July 26, 2009

why is the sky and ocean blue?

I recently went on a 9 day cruise to the Caribbean. Nine days is a long time to be surrounded by water. My family and I spent a lot of time on the back of the boat watching the propellers churn up beautiful pale blue water and left me thinking about why it's blue.  I also decided to find out why the sky is blue because well... why not? 

Lets start with the ocean - 

The ocean is blue because the water absorbs the colors in the red end of the light spectrum. Since everything else is absorbed all we see is blue. 
*The ocean can also appear green or red as light bounces off of floating sediment in the water. 

The sky -

Blue sky is the result of rayleigh scattering. As light passes through the atmosphere, longer wave lengths pass through unaffected. Shorter wave lengths are absorbed by gas molecules and the light is radiated in all directions. Since this rayleigh scattering is happening all over the sky, what you see is a blue sky. 

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