Saturday, November 04, 2006

Why are sunsets red?

This evening we saw a fantastic sunset - bright yellows, reds and oranges. This prompted my daughter to ask why sunsets in Africa are supposed to be the best sunsets, and generally why sunsets are red and orange.

To understand why the sky goes red just before the sun goes down we also need to understand why the sky is blue for the rest of the time. We are familiar with the sky usually being blue so we tend to think that red sunsets must be caused by 'something else', and accept that the sky 'just is' blue.

Red and blue are words we use to describe different colours (or wavelengths) of light, so that gives us a clue; at different times of the day we are seeing different wavelengths of sun light. When the sun is low down on the horizon (rising and setting) the sky is red, and when the sun is higher in the sky we see blue light.

So, what changes between the sun being low down and high up in the sky? To find out, visit our new page, sunsets, and learn why the sky changes colour.

The Geography Site


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