The apparent contradiction that if the universe is infinite, eternal, and uniformly filled with stars, then every line of sight should end on a star's surface, making the night sky as bright as the Sun. The dark night sky suggests the universe has finite age or other limiting factors.
Named after German astronomer Heinrich Olbers who discussed it in 1823, though the paradox was noted earlier by others including Kepler and Halley. 'Paradox' comes from Greek 'paradoxon' meaning contrary to expectation.
Olbers' paradox is beautifully resolved by the Big Bang—the universe simply hasn't existed long enough for light from infinitely distant stars to reach us, and cosmic expansion redshifts distant light beyond visible wavelengths! The darkness between stars is actually evidence that our universe had a beginning and is still young on cosmic scales.
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