Why does sky appear blue and cloud appear white?

Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.

First, let’s talk about the composition of a cloud. Clouds are composed of tiny round water droplets, which form when water vapor condenses from a gas to a liquid.  

Next is the electromagnetic spectrum. The sun emits energy over a wide rangem and humans aren't able to see most of that energy with the naked eye. We're only able to see the visible spectrum: red, orange, yellow, green, blue and violet light. When those colors are combined, we see white light.  

As the sun’s light passes through these small cloud droplets, it scatters. In other words, it’s pushed out of the droplet in all different directions.  

Unlike scattering in the sky or ocean, in which molecules are so small they only scatter blue and violet light, water droplets are large enough the scatter the entire spectrum.  

That's why clouds appear to be mostly white.  

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