So, today's Google doodle celebrates the 340th anniversary of Ole Rømer's (somewhat approximate) determination of the speed of light by observing the eclipses of Jupiter's moon Io.Is there a flat earth model under which this would have been possible - by which I mean not just the observations of Io, but also the application of the geometry of the solar system then to approximate the speed of light? Or was the hapless Dane fooled into thinking he was doing something he wasn't?