Science
Oceans and Seas
Oceanography
Air Pollution

Why is the sky and sea blue?

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Wiki User
2012-09-01 03:51:43

1. Outer space contains virtually no gas/dust to scatter

light.

Outer space is black.

2. The sky is blue because that's the colour of air (mostly

nitrogen), which is not totally colourless. You can see this effect

looking at distant (10 km-plus) mountains. They have a blue tinge

(caused by the intervening air between you and the mountains) known

as atmospheric perspective.

3. If the sky's colour was due to reflection from the oceans,

then it would be white above Antarctica, which is snowy white.

4. If the ocean was blue because it reflects the sky, why does

it still look blue-ish when under a totally clouded-over sky?

5. Why blue? Light scattering by the atmosphere (Rayleigh

scattering) has most effect on the most energetic light. The most

energetic light is that with the highest frequency/shortest

wavelength.

6. So, while all light is scattered, blue light is scattered the

most, so the atmosphere "captures" more of the blue light, letting

more of the red light through, and the atmosphere is coloured blue

by that "captured" light.

7. If there were *no* selective scattering, and all wavelengths

were scattered *equally*, the sky would appear white.


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