Olbers's paradox

Problem discussed in 1826 by German doctor, mathematician, and astronomer Heinrich Olbers, though it had been considered by several thinkers previously. It poses the question: If the universe is infinite in extent and filled with stars, why is the sky dark at night? Several factors contribute to the resolution of the ‘paradox’. The universe is not infinitely old: the Big Bang occurred approximately 14 billion years ago, so we can (roughly speaking) only observe a region of 14 billion light-years' radius, not an infinite region. In addition, the expansion of space since the Big Bang results in the cosmological red shift, which weakens the intensity of radiation from distant cosmic objects.