Short · Sky
Why does Mars seem to move backward?
Every two years or so, Mars stops, loops back west and carries on. It isn't reversing: Earth, on the inside track, is overtaking it, as it does around February 19, 2027.
Try it yourself
Opens Mars Loop. Change the same thing yourself.
Transcript
Why does Mars seem to move backward? Most nights, Mars drifts east against the stars. But every two years or so, it stops, loops back west for two or three months, then carries on. Mars isn't reversing. We're overtaking it. Earth is on the inside track and moves faster. As we pass, Mars seems to slip backward, like a slower car on the highway. Now drag the date to February nineteenth, when we pass it. Try it yourself at Explainer Tools dot com.