Question: How come the sky is blue butspace is black?

Jen Gupta answered on 14 Jun 2011:

Great question! The sky is blue during the day because of the Earth’s atmosphere and the process that makes the sky blue is called Rayleigh scattering. What we think of as white light is actually made up of different colours. You can see this if you shine light through a prism. If we think of light as a wave, each colour has a different wavelength, i.e. the distance between two peaks. Red light has the longest wavelength and blue light has the shortest wavelength. When light travels through the Earth’s atmosphere, the light waves bump into the gas particles and change the direction they are travelling in. This is called scattering. The amount of scattering depends on the wavelength – blue light has the shortest wavelength and is scattered the most. This makes the sky look blue during the day. At sunset, light has to travel through more of the atmosphere to get to us. This lets other longer wavelengths be scattered as well so the sky looks red.

In space there’s no atmosphere to scatter any light so it looks black.