Question

which describes one way that aristarchuss explanation of the movement of objects in the sky was different from other scientists earlier explanations?
he discovered venuss phases
he argued that earth rotates on its axis.
he explained the concept of retrograde motion.
he described the epicycles of the planets in the sky

Explanation:

Aristarchus was an ancient Greek astronomer. Earlier explanations often had Earth as the center (geocentric). Aristarchus proposed that Earth rotates on its axis. Galileo discovered Venus's phases. Ptolemy explained retrograde motion using epicycles. So the key is comparing Aristarchus' unique idea.

Answer:

He argued that Earth rotates on its axis.