Labs / Astronomy
Mars Retrograde Loop
On the left, Earth and Mars circle the Sun; on the right is the path Mars traces across the fixed stars as we watch it from a faster-moving Earth. Press play (or step through time) and notice that near opposition — when Earth passes between the Sun and Mars — the red planet slows, reverses into a backward loop, then resumes its eastward drift.
Earth 0°Mars 0°λ 0°Prograde
What to try
- When does Mars switch from prograde to retrograde — is it exactly at opposition, or a little before?
- Earth never actually reverses. So what makes Mars look like it moves backward across the sky?
- Watch the heliocentric view during the loop: where is Earth relative to Mars each time the motion flips?
- Why does the apparent path curl into a loop instead of just sliding back and forth along a line?
- Mars looks biggest and brightest during retrograde. What does the orbit view say about their distance then?