Here's an explanation for the retrograde motion of the planet Mars. Before dawn breaks tomorrow for people in the United States, the planet Mars will begin its retrograde motion. Early stargazers thought Earth was the center of the universe. Now we know that all the planets orbit the sun. When you pass another car, sometimes you notice the illusion of that car seeming to move backwards with respect to the distant landscape.
Earth moves faster in orbit than Mars.
A month from now, we'll pass between Mars and the sun. With thanks for the National Science Foundation, we're Block and Byrd for Earth and Sky.