The Universe — Describe

Describe what is meant by redshift.

Redshift is the increase in the observed wavelength of electromagnetic radiation (light) received from a star or galaxy that is moving away from (receding from) the observer, compared with the wavelength that would be observed if the source were stationary. The light's wavelength is shifted towards the red (longer-wavelength) end of the spectrum. The faster a galaxy is receding, the greater its observed redshift. Since almost all distant galaxies show redshift, and more distant galaxies show greater redshift, this provides evidence that the Universe is expanding, with galaxies moving apart from each other.