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Ole Romer (1644-1710), Danish astronomer. Romer's name is also spelt Olaus Roemer. He is best known for his measurements of the speed of light. He carried out this calculation in 1676, proving that the speed of light had a finite value and was not infinite. He did this by observing eclipses of Io, a moon of Jupiter. This gave him an estimate of the time light took to travel across the large distances of the solar system. His result was around a quarter less than the actual value, but this key advance was accepted by fellow scientists Huygens and Newton. Illustration published in 1913 in the Journal of the Royal Astronomical Society of Canada (courtesy of Popular Astronomy).
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