Suppose Rømer had used Saturn and one of its satellites instead of Jupiter and Io to measure the speed of light. How would his measurements have compared with those for Jupiter?
A) The measured time discrepancy between predicted and measured values for a given eclipse would have been shorter for Saturn.
B) The measured time discrepancy between predicted and measured values for a given eclipse would have been the same for Saturn.
C) The measured time discrepancy between predicted and measured values for a given eclipse would have been longer for Saturn.
D) Rømer could not have made such a measurement because Saturn had not yet been discovered.

Question

Quizplus · Accepted Answer

Saturn is farther from the Earth than Jupiter, so the light from Saturn's satellites takes longer to travel to Earth. This would result in a longer measured time discrepancy for a given eclipse when Earth is moving away from Saturn compared to when using Jupiter and Io, because the additional distance would amplify the observable effects of the finite speed of light.

Suppose Rømer Had Used Saturn and One of Its Satellites