Satellites and the Moon: Orbiting Earth
Simulation Description
This simulation models artificial satellites and the Moon in orbit around Earth, directly supporting the AQA GCSE Physics topic of space physics (Paper 2). It shows all four orbital objects simultaneously in a 3D space environment — two LEO satellites racing around in inner cyan orbits, a GPS-altitude MEO satellite in green at middle distance, a geostationary GEO satellite in yellow barely moving at high altitude, and the Moon in a bright lavender orbit far beyond all of them.
Earth is rendered with a simplified but recognisable surface — blue oceans, green continental landmasses, polar ice caps, and a soft blue atmospheric glow. The scene is lit by a directional sun, so all objects are illuminated from the same direction. A star field of 3,500 points surrounds the scene.
The simulation teaches three connected principles. First, that gravity keeps all orbiting bodies in orbit — without it they would travel in a straight line. Second, that lower orbit means higher orbital speed and shorter period — students can watch the two LEO satellites visibly lap the GEO satellite over and over, while the Moon barely moves in comparison. Third, that period and altitude are not simply proportional — the difference between a 92-minute LEO orbit and a 27.3-day Moon orbit is dramatic and counter-intuitive until students see it live.
The comparison card (top-right, always visible) shows altitude, period, and speed side by side for the selected satellite type and the Moon. Clicking LEO, MEO, or GEO in the bottom strip highlights that orbit type with a brighter ring and larger satellite, and the focus panel shows its real-world data including examples, orbital speed, and a key fact. Toggling 🏷 Labels opens the focus panel and adds the five-step chip sequence cycling through the core physics, plus a label and altitude for the Moon, and dashed gravity force arrows pointing from each object toward Earth.
Students can drag to orbit the scene from any angle, scroll or pinch to zoom, and pan with right-click drag or two-finger movement to slide across the full range from LEO to the Moon’s orbit. The speed slider ranges from ⅟₂₀× (slow enough to watch a single GEO orbit) to 18× (fast enough to count LEO laps in seconds).
Suggested Class Activity
“Why Does the Moon Take So Long?” — Orbital Speed and Period Investigation Suitable for: GCSE Physics Year 10/11 — Space Physics, orbits and gravity. 25–30 minutes.
Setup (2 min) Open the simulation. Labels off. Speed at 4×. Ask students to watch for 30 seconds before doing anything.
Stage 1 — Observation (4 min) Ask: “Without looking at any numbers — which objects are moving fastest? Which is slowest?” Students write their ranking on mini whiteboards.
Most will correctly rank LEO fastest, Moon slowest. Then reveal the comparison card by clicking LEO. Ask: “The LEO satellite is 400 km above Earth. The Moon is 384,400 km away. That is almost 1,000 times further. Does the Moon travel 1,000 times more slowly?” Target: no — it is about 7.5 times slower, not 1,000 times. The relationship is not linear; it follows Kepler’s third law (not required for GCSE, but the observation plants the seed).
Stage 2 — Period prediction (6 min) Students predict which of the following has the longer period, and by roughly how much:
| Comparison | Predict longer | Predict ratio |
|---|---|---|
| LEO (400 km) vs MEO (20,200 km) | ? | ? |
| MEO vs GEO (35,786 km) | ? | ? |
| GEO vs Moon (384,400 km) | ? | ? |
Click each orbit type and read the periods from the comparison card to check. Ask: “What pattern do you notice between altitude and period?” Target: higher altitude → longer period. Going from LEO to Moon is a factor of ~215 in period but only a factor of ~960 in distance.
Stage 3 — Why does GEO matter? (5 min) Set the speed to ½× and select GEO. Ask students to watch the GEO satellite relative to a fixed point on Earth for 10 seconds. Ask: “What do you notice about where it is above Earth?” Target: it appears to stay above the same point — it is geostationary.
Ask: “Why is this useful for TV satellites?” Target: a dish on your roof can point at a fixed spot in the sky and receive a signal without tracking. Compare to LEO satellites (the ISS passes overhead in minutes, you cannot track it with a fixed dish).
Stage 4 — Gravity discussion (5 min) Toggle 🏷 Labels on. Draw students’ attention to the dashed arrows pointing from each object toward Earth. Ask: “What do these arrows represent? Why are they all pointing in the same direction?” Target: gravitational attraction — every orbiting body is constantly being pulled toward Earth. This pull is the centripetal force that keeps the orbit circular. Without it, each object would continue in a straight line into space.
Ask: “The Moon is much further from Earth than the satellites. Does gravity still work at that distance?” Target: yes — gravity acts over any distance, it just gets weaker. A weaker pull at greater distance means a slower orbit and a longer period.
Stage 5 — Written explanation (5 min) Students answer: “Explain why a satellite in low Earth orbit has a shorter orbital period than the Moon.”
A strong GCSE answer will include: the satellite is closer to Earth → gravitational force is stronger → the satellite must travel faster to maintain orbit → shorter circumference + higher speed → shorter period. The Moon is much further away → weaker gravitational force → slower orbital speed → much longer period.
Adaptation notes
- For lower-confidence learners: leave labels on throughout; use the chip sequence as a writing frame; focus only on the LEO vs Moon comparison and skip MEO/GEO
- For higher ability: ask students to use the data from the comparison card to test whether doubling the altitude doubles the period; they will find it does not, opening discussion of the inverse-square nature of gravity
- For SEND learners: extra-slow mode at ⅟₂₀× makes a single LEO orbit last long enough to watch and count; the reading ruler supports use of the comparison card; zoom and pan allow students to examine individual orbits at their own pace without the full scene being overwhelming