which idea did ptolemy’s model use to explain why the planets appeared to move backward as they moved in their orbits? the planets spun in epicycles. the planets rotated on their axes. the planets revolved around the sun. the planets were made of different materials.
Answer: Ptolemy’s model used the idea of “the planets spun in epicycles” to explain why the planets appeared to move backward as they moved in their orbits. Ptolemy, a Greek astronomer and mathematician, proposed an Earth-centered geocentric model of the solar system known as the Ptolemaic system. In this model, the planets moved along small circular paths called epicycles while the centers of these epicycles moved around the Earth on larger circles, which was an attempt to account for the observed retrograde motion of the planets.