Galileo observed Venus to go through a full range of phases. Which other planet should also display a full range of phases when viewed from Earth?
A) Mercury
B) Mars
C) Jupiter
D) any other planet

Question

Quizplus · Accepted Answer

Mercury, like Venus, orbits closer to the Sun than Earth does. Therefore, from Earth, we can see Mercury go through a full range of phases similar to the Moon's, from new to full, as its position relative to Earth and the Sun changes. This is due to the geometry of its orbit relative to Earth's. Planets that orbit further from the Sun than Earth, such as Mars, Jupiter, etc., do not show a full range of phases to observers on Earth.

Galileo Observed Venus to Go Through a Full Range of Phases