How did Copernicus know Mercury was closer to the Sun than Earth?
A) It can always be seen relatively close to the Sun.
B) He measured the period and used Kepler's third law.
C) He observed it passing through a crescent phase.
D) It can be high in the sky at midnight.

Question

Quizplus · Accepted Answer

Mercury is always observed close to the Sun in the sky, indicating it orbits closer to the Sun than Earth does.

How Did Copernicus Know Mercury Was Closer to the Sun