See why the Moon keeps one face toward Earth - toggle tidally locked synchronous spin versus an unlocked spin that reveals the far side while you scrub the orbit.
Play orbit advances one circuit in about 16 seconds at 1x; pause and scrub 0 to 100 percent to hold the Moon while you compare locked versus unlocked faces.
The Moon's spin equals its 27.32-day sidereal orbit, lunar recession is about 3.8 cm/yr, and Earth's day lengthens about 1.7 ms/century. This is an educational geometry visualization, not a tidal-friction solver.
Tidal Locking 3D Explorer
See why the Moon keeps one face toward Earth - toggle tidally locked synchronous spin versus an unlocked spin that reveals the far side while you scrub the orbit.
Drag to orbit the view, scroll or pinch to zoom, and press Play orbit. Switch Tidally locked (spin equals the 27.32-day orbit) or Unlocked spin to watch the near-side marker leave Earth-facing orientation.
The facts panel lists Moon spin = orbit 27.32 d, lunar recession 3.8 cm/yr, and Earth day lengthening 1.7 ms/century from NASA and lunar laser ranging references.
- Earth and Moon with a near-side marker on the lunar disk
- Tidally locked versus Unlocked spin presets
- Orbit phase scrub 0 to 100 percent plus Play orbit / Pause orbit
- Published tidal figures in the facts panel
- Compressed-scale disclosure so the table carries the real numbers
- Runs fully in the browser with the vendored three.js engine - no account, no upload
Teachers use it to show synchronous rotation in one glance, students compare locked and unlocked faces, and curious readers pause mid-orbit to read recession and day-lengthening rates.
| Quantity | Value | Source |
|---|---|---|
| Moon spin = orbit | 27.32 d sidereal | NASA Moon Fact Sheet |
| Lunar recession | 3.8 cm/yr | Lunar laser ranging |
| Earth day lengthening | 1.7 ms/century | Tidal friction rate |
Everything renders on your device with WebGL. The 3D engine loads once (about 0.7 MB) and is cached; no scene data is sent to a server.
The scene is an educational geometry visualization - it does not solve tidal friction equations and is not a physical simulation of how the Moon locked over deep time.
For a step-by-step walkthrough, read the Tidal Locking 3D Explorer step-by-step guide. The Space 3D collection also includes a Moon Phases 3D Explorer for lit-fraction geometry and a Exoplanet Transit 3D Explorer for transit depth.
Frequently Asked Questions
What does Tidal Locking 3D Explorer show?
Earth and the Moon on a compressed orbit. In Tidally locked mode the Moon rotates once per 27.32-day sidereal orbit so the near-side marker stays Earth-facing. Unlocked spin multiplies the spin so the far side appears.
How is this different from Moon Phases 3D Explorer?
Moon Phases 3D Explorer teaches lit fraction from Sun-Earth-Moon geometry. Tidal Locking 3D Explorer teaches synchronous rotation - why one face stays toward Earth - with recession and day-lengthening figures in the panel.
What do 3.8 cm/yr and 1.7 ms/century mean?
Lunar laser ranging measures the Moon moving away about 3.8 cm per year. Tidal friction also lengthens Earth's day by about 1.7 milliseconds per century. Both are published rates shown in the facts table.
Is this a tidal physics simulation?
No. The scene is an educational geometry visualization with compressed sizes and distances. It does not integrate tidal torque equations or predict deep-time lock history.
Does Unlocked spin match a real Moon state?
No. Unlocked spin is a didactic contrast so you can see what a free-spinning satellite would look like. Today's Moon is tidally locked.
Does Play orbit use the real 27.32-day period?
No. Orbit animation compresses time for classroom pacing. The published 27.32-day figure appears in the table; the slider and play button are for geometry only.