It is this region in which the Earth overtakes Mars that we get retrograde motion. Using a heliocentric model makes for a simple explanation of the retrograde motion of Mars.

"The explanation for retrograde motion in a heliocentric model is that retrograde occurs roughly when a faster moving planet catches up to and passes a slower moving planet," StarChild explains.

Additional resources To read more about the heliocentric model, and to learn about retrograde motion, visit this page at the Penn State University College of Earth and Mineral Sciences website.

Nicolaus Copernicus made sense of Mercury’s retrograde motion—and that of the outer planets, too—back in 1543 with that heliocentric model.

In the 16th century, Copernicus revived interest in Aristarchus’s heliocentric ideas, noting that the most puzzling aspect of planetary motion, the periodic “retrograde” motion of the ...

His model has the planets moving around the Sun in circular orbits. This can explain retrograde motion, but his model doesn't fit all the planetary position data that well.

We’re in Mercury retrograde. Here’s what that really means. The planet’s apparent backward motion occurs for a few weeks about every four months. Here’s what’s really happening—and how ...

What we are talking about is apparent retrograde motion, when to us on Earth it looks like a planet is moving across the sky in the opposite direction to its usual movement.

Today, I wanted to talk about the history of the heliocentric model. After all, Copernicus’ most notable accomplishment is probably his proposed heliocentric, or sun-centered, model for the ...