Why Is the Night Sky Dark?

Olbers' paradox: dark sky as evidence of cosmic entropy gradient

Static Universe

In an infinite, static universe every line of sight eventually reaches a star. The sky should be uniformly bright. The night sky is dark.

In a young, expanding universe a finite age and finite stellar lifetimes leave most sightlines empty. Expansion adds a secondary effect: the most distant light is redshifted beyond visibility.

The darkness of the night sky is not emptiness.
It is evidence that the universe had a beginning, is expanding,
and that distant light has been stretched beyond visibility.

core conceptemergent / positiveconstraint / breakdown