On this day in 1872 – May 6th – Dutch astronomer and mathematician Willem de Sitter was born.

He is best remembered for his contributions to cosmology, in particular for showing that a universe containing very little matter would expand. This paved the way for later research carried out by the American astronomer Edwin Hubble who was to provide observational evidence that the universe is expanding. De Sitter's work was honored with two prestigious awards, the Gold Medal of the Royal Astronomical Society and the Bruce Medal of the Astronomical Society of the Pacific.

Mona Evans
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