Trivia: What happens when a planet loops back in its trajectory across the sky?
Scintillation
Retrograde
Backstroke
Apastron
The correct answer is Retrograde
So why is this answer correct? : When tracing the motion of the planets across the sky from Earth, some of the planets will occasionally loop back in their trajectory. This retrograde motion baffled early astronomers for centuries, but today we know the motion is caused by Earth’s position in the solar system surpassing the other planets in their orbits around the sun.