Why Is the Sky Blue?
We often say, “The sky is blue because it reflects the blue colour of the ocean.”
It sounds convincing—but it isn't the reason.
The sky is blue because sunlight, while passing through our atmosphere, encounters tiny molecules of gases. The shorter wavelengths of light, particularly blue, are scattered much more strongly than the longer wavelengths such as red.
That scattered blue light reaches our eyes from all directions.
The oceans can look blue for several reasons, including the way water absorbs and scatters light, but the blue sky does not come from the sea being reflected upward.
And there is a lovely connection: at sunrise and sunset, sunlight travels through much more atmosphere. Much of the blue light gets scattered away before reaching our eyes, leaving more red, orange and pink light.
So the next time we see a blue sky, we are really seeing sunlight interacting with the Earth's atmosphere.
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