Google Doodle commemorates the 340th anniversary of Ole Rømer determining the speed of light

Google is commemorating the 340th anniversary of the Determination of the Speed of Light. The discovery was reported on 7 December 1676 by the first scientific journal in Europe, the Journal des sçavans. The Journal is still operating, in a modern form known as Journal des Savants. Danish Astronomer Ole Rømer was observing the eclipses of Jupiter’s moon Io. Rømer found a discrepancy in the predicted and actual appearances of the eclipses. In an announcement to the Royal Academy of Sciences  in Paris, Rømer predicted that the Io would come out of the shadow of Jupiter ten minutes after it was anticipated, on 16 November 1676. Instead of the speed of light, Rømer was more interested in explaining the discrepancies of the emergence or immersion of IO during its eclipses.  Rømer calculated that it would take roughly ten to eleven minutes for light to travel a distance equal to half the diametre of a terrestrial orbit. This estimation works out to 220,000 kilometres per second, a value that is twenty six percent below the actual value. Rømer rightly predicted that light had a finite speed, which was itself not yet established in the scientific community. While Google is commemorating Ole Rømer determining of the speed of light, it was only an indirect inference of his findings. There is some debate over who exactly should be credited for the discovery, with some scientists preferring to credit Christiaan Huygens who calculated the approximate speed of light in Earth based units.