GRE Reading Comprehension
Source: magoosh reading hard
Galileo's drawings show that he first observed Neptune in 1612, and again in 1613. On both occasions, Galileo mistook Neptune for a fixed star when it appeared very close—in conjunction—to Jupiter in the night sky; hence, he is not credited with Neptune's discovery.
During the period of his first observation, Neptune was stationary in the sky because it had just turned retrograde that very day (retrograde refers to the apparent backward motion created when the orbit of the Earth takes it past an outer planet). Since Neptune was only beginning its yearly retrograde cycle, the motion of the planet was far too slight to be detected with Galileo's small telescope.
According to the passage, all of the following can account for Galileo's inability to identify Neptune as a planet EXCEPT?
- A The direction in which Neptune rotates
- B A shift in the orientation between Neptune and the Earth
- C The almost indiscernible distance between Neptune and Jupiter
- D The condition of Galileo's instruments
- E The fact that Neptune's lack of motion suggested another celestial phenomenon
Correct Answer: A