What celestial body was key to Rømer's speed of light measurement?
The Sun
Mars
Jupiter's moon Io
Venus
Answer
Jupiter's moon Io played a crucial role in Rømer's groundbreaking measurement of the speed of light. By observing the eclipses of Io by Jupiter, Rømer noticed a discrepancy in the timing of the eclipses depending on the relative positions of Earth and Jupiter.
Stargazing Through Time: The Ole Rømer Astronomical Challenge