Caption: An animation illustrating Olbers' paradox (AKA dark night sky paradox) by filling the sky with stars and making the sky as bright as a star everywhere you look.
Features:
Since we do NOT observe this super bright sky, one or more of the 4 assumptions is wrong.
Big Bang cosmology gives two causes for the blackness of space:
Counterfactually if it were in thermodynamic equilibrium, all astro-bodies would be at one temperature and the radiation field in space would be a blackbody radiation field at that one temperature.
The heating up is a manifestation of the 2nd law of thermodynamics: photons are spontaneously (via random processes) flowing from the photon-dense environment inside stars to the photon-undense environment in space.
If the Λ-CDM model is correct to infinite cosmic time (which is a wild extrapolation), the stars will NEVER succeed in heating up the radiation field in space and, in fact, thermodynamic equilibrium will be achieved at absolute zero asymptotically as cosmic time goes to infinity. This grand finale is the heat death of the universe.