An idea often taken advantage of by proponents of creationism that light has been gradually slowing down with time. When one looks at galaxies that are further away, the light that arrives is redshifted. The further away the galaxy, the greater the redshift. Cosmologists explain this as the expansion of the universe, with things that are further away moving more rapidly.

The tired light theory, tries to explain this phenomenon by saying that the objects are not moving away, but that light is slowing down, causing the wavelength to red shift. However, this still does not explain the background radiation levels of the universe, which have the spectral shape of a black body. Furthermore, the speed of light is more than a quantity for light, its a fundamental constant that enters into a number of other physical laws.

Log in or register to write something here or to contact authors.