(London Independent) A theory that explains why it gets dark at night – dismissed by scientists for 200 years – has been proved right by new research using images from the Hubble Space Telescope.
German astronomer Heinrich Olbers famously pondered the "dark sky paradox": if there was an infinite number of stars in the universe, how could it get dark at night as every point in the sky would contain a star.
He suggested clouds of hydrogen could be blocking the light.
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But later astronomers estimated there were actually 100 to 200 billion galaxies in the observable universe – not enough to fill the sky – so this theory was not needed to explain why it gets dark.