What did you change in the model?
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.
Labs / Astronomy / Mars Retrograde Loop
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.
Why it matters
Why explore this?
Astronomy uses patterns in light and motion to explain objects we cannot touch directly. This model lets you change one part of a space system and see what the evidence would look like.
Explore
Try the model
Earth 0°Mars 0°λ 0°Prograde
Investigate
Questions to test
Predict first, try it in the model, then use what you observe to answer.
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?
Explain
Make sense of what happened
Look for a cause-and-effect rule: what did you change, what responded, and what stayed the same? Astronomers use those patterns to infer how distant systems work.
Check
Before you leave
What visible evidence changed?
What rule could explain that change?
If you can answer all three using evidence from the model, you understand the main idea. If not, return to Explore and change one setting at a time.