Paradox of why the sky is dark at night.
If the universe is endless and uniformly populated with luminous stars, every line of sight must end at the surface of a star and the night sky should be bright with no dark spaces between stars. This paradox is widely attributed to Heinrich Wilhelm Olbers (17581840), who discussed it in 1823, though Johannes Kepler first advanced the problem in 1610 as an argument against the notion of a limitless universe with infinite stars. The paradox has since been resolved: we can see no farther than the light-travel distance within the lifetime of the universe, and light becomes redshifted to invisibility (see redshift ).