Why is the sky blue?
Do you sometimes ask yourself, why is the sky blue? Here’s the answer. As white light passes through our atmosphere, tiny air molecules cause it to ‘scatter’. The scattering caused by these tiny air molecules (known as Rayleigh scattering) increases as the wavelength of light decreases.
Violet and blue light have the shortest wavelengths and red light has the longest. Therefore, blue light is scattered more than red light and the sky appears blue during the day. When the Sun is low in the sky during sunrise and sunset, the light has to travel further through the Earth’s atmosphere. We don’t see the blue light because it gets scattered away, but the red light isn’t scattered very much – so the sky appears blue.
During sunrise or sunset, the sky appears to change colour. When the Sun is low in the sky, the light has to travel a longer distance through the Earth’s atmosphere so we don’t see the blue light because it gets scattered away.
Instead we see the red and orange light that travels towards us since this light hasn’t been scattered very much. Hence the sun and skies look blue during the day, and redder at night.
Now you know why the sky is blue.