Scrub the slider to watch the Moon's orbit widen and Earth's day lengthen: laser ranging off mirrors the Apollo astronauts left on the Moon shows it receding about 3.8 cm per year (NASA/JPL), a slow drift with a measurable knock-on effect on how long a day lasts.
Published figures: mean Earth-Moon distance today is 384,400 km; the day-length trend is about 1.7 milliseconds per century, an average drawn from paleontological growth-ring records. The slider projects those measured rates forward and backward across geologic time.
Earth-Moon Orbit Recession Explorer
Last reviewed: 2026-07-29 | Authored by the FreeToolOnline teamWatch the Moon recede from Earth at 3.8 centimeters per year, projected across 1 billion years. Tidal friction between the two bodies continuously transfers angular momentum, pushing the Moon into a larger orbit while slowing Earth's rotation. Use the time slider below to scrub through deep time and see how the projected day length grows past today's 24 hours as the orbit widens.
Key Features
- 1-billion-year time scrub: Move the slider to advance or rewind through orbital evolution.
- Real published figures: Moon recession rate 3.8 cm/year from Apollo laser retroreflectors; day-length increase 1.7 milliseconds per century from tidal-dissipation models.
- Educational approximation: The visualization shows the dominant tidal-friction effect; it does not solve the full three-body problem or account for orbital complexities like perturbations from other bodies.
- No accounts needed: Runs fully in your browser; your data never leaves your device.
Why the Moon Recedes
Tidal friction arises because Earth's rotation is faster than the Moon's orbit. The tidal bulge on Earth (raised by the Moon's gravity) leads the Moon's position, pulling it forward gravitationally. This accelerates the Moon and transfers energy from Earth's rotation to the Moon's orbit. Over deep time, the Moon spirals outward while Earth's day grows longer.
Long-Term Evolution
| Current Moon distance | 384,400 km (about 30 Earth diameters; measured via Apollo laser retroreflectors) |
| Recession rate | 3.8 centimeters per year |
| Earth's current day length | 24 hours |
| Day lengthening | 1.7 milliseconds per century |
| Future distance (1 billion years) | About 422,400 km (38,000 km more distant) |
| Future day length (1 billion years) | About 28.7 hours, projecting today's measured rate forward at a constant pace (full tidal lock near 47 hours is a separate, tens-of-billions-of-years outcome - see FAQ) |
Privacy + How It Runs
The Earth-Moon Orbit Recession 3D Explorer runs entirely in your browser using WebGL and the vendored three.js engine. No data is sent to any server. Geometry is procedural (generated in code), and all calculations happen on your device. The facts panel displays real published figures from NASA, ESA, and peer-reviewed tidal-evolution models.
The Space 3D collection also includes Earth-Moon Barycenter 3D (the instantaneous balance point the two bodies orbit right now) and Tides: Earth and Moon 3D (the daily tidal bulge, not this page's multi-million-year drift).
Frequently Asked Questions
How do we know the Moon recedes at 3.8 centimeters per year?
Apollo astronauts placed laser retroreflectors on the Moon, and scientists have measured the distance from Earth to those mirrors for over 50 years. The precision is remarkable - accurate to within a few millimeters - and confirms the 3.8 cm/year recession rate. This direct measurement is the gold standard in planetary science.
What happens to the Moon in the far future?
Eventually, the Moon and Earth will become tidally locked to each other, meaning they always show the same faces to one another - the Moon stops receding, and Earth's day becomes about 47 hours long (equal to the Moon's orbital period). This steady state would last billions of years. However, the Sun will expand into a red giant in about 5 billion years, potentially disrupting the Earth-Moon system long before that happens.
Is this a physics simulation, or an approximation?
This is an educational approximation tuned to show the dominant tidal-friction effect. It does not solve Einstein's field equations or account for the full complexity of Earth's interior (layering, viscosity, mantle convection affect tidal heating). Real tidal dissipation is modelled by geophysicists using complex digital simulations; this explorer shows the key trend - recession over time - in an accessible way.
Why does a faster rotation pull the Moon outward?
Earth rotates faster than the Moon orbits, so the tidal bulge on Earth's surface leads the Moon's position in the sky. This misalignment pulls the Moon gravitationally forward in its orbit, accelerating it. By Newton's laws, acceleration means the Moon gains energy and spirals outward. Meanwhile, the gravitational "drag" slows Earth's rotation, transferring angular momentum from Earth's spin to the Moon's orbit.
How does this affect us today?
The practical effect is tiny per human lifetime - only 3.8 centimeters per year. But over geological timescales, it shapes the ocean's tidal strength (weaker tides as the Moon moves away), day length, and the history of life. Paleontological records show that ancient days were shorter; 400 million years ago, days were only about 23 hours.
Why does the view in the slider show tidal evolution in *reverse* (going back in time)?
The slider spans backward into the past - moving it to the right goes further into the future, showing the Moon at a greater distance and Earth's day much longer. This lets you visualize how the system evolves if you "play forward" from today into the next billion years of tidal evolution.