Our little startup started it's life at Ole Römers väg (Ole Roemer's road) in Lund, so I've looked up a few versions of this story. The one I like the best* has

Our little startup started it's life at Ole Römers väg (Ole Roemer's road) in Lund, so I've looked up a few versions of this story. The one I like the best* has a more dismal tone: Ole discovered the finite speed of light, but was outmaneuvered by Jean-Dominique Cassini who had a complex theory based on tables. I sometimes use it when I want to explain how important it is to try and see past "social truth" to find the real one. I can's say which version is more accurate, but there's a scientific inaccuracy in the OP that makes me a bit skeptical of the author: The distance between Jupiter and the Earth will have no impact on how long Io is hidden behind Jupiter. It's the change in distance been Jupiter and Earth from when Io disappears behind Jupiter to when it reappears some minutes later that will affect the timing. So IMHO the illustration in the OP is wrong, the timing will be approximately the same in position 1 and 2. Position 2 should be moved so that it is at the far right (or left) of Earths orbit. (*) http://www.pbs.org/wgbh/nova/physics/ancestors-einstein.html http://www.pbs.org/wgbh/nova/physics/ancestors-einstein.html