Why is the sky blue (and why red at sunset)?

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Have you ever wondered why the sky looks blue?  This happens because of the light from the sun and the earth’s atmosphere!

First of all let’s speak about the light. The light from the sun looks white. But it is really made up of all the colors of the rainbow.  All light travels in a straight line unless something gets in the way, like molecules of the gases in the atmosphere. In this case the light is being scattered.

Sunlight reaches Earth’s atmosphere and is scattered in all directions by all the gases and particles in the air. 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. The characteristic blue color of the sky would be black without the Earth’s existing atmosphere.

Why does the sky become red at sunset?

As the sun gets lower in the sky (before sunset), its light is passing through more of the atmosphere to reach you. Even more of the blue light is scattered, allowing the reds and yellows to pass straight through to your eyes. This is what makes a red sunset!

Citation: NASA, Wikipedia

Before you go, remember that in our website you can find additional brief & interesting facts!