Rømer calculated the speed of light by observing the large moons of Jupiter being eclipsed by Jupiter while that planet was at opposition and while it was at superior conjunction. How large is the difference in the Jupiter-Earth distance when Jupiter is at opposition and when it is at superior conjunction?
A)1 au
B)2 au
C)1 ly
D)0 au

Question

Quizplus · Accepted Answer

When Jupiter is at opposition, it is on the same side of the Sun as the Earth, and so the Jupiter-Earth distance is at a minimum. When Jupiter is at superior conjunction, it is on the opposite side of the Sun as the Earth, and so the Jupiter-Earth distance is at a maximum.

The difference between the maximum and minimum distances is equal to the diameter of the Earth's orbit around the Sun, which is 2 astronomical units (au) or approximately 300 million kilometers.

Rømer Calculated the Speed of Light by Observing the Large