Asger Risom
The change is invisible year by year, but over millennia it could lengthen our days, alter tides, and even bring an end to total solar eclipses.
The change is invisible year by year, but over millennia it could lengthen our days, alter tides, and even bring an end to total solar eclipses.
Earth’s Closest Neighbor
The Moon, orbiting about 384,400 kilometers away, is Earth’s constant companion. Its gravitational pull influences tides, stabilizes our planet’s tilt, and has shaped life for billions of years.
A Subtle but Real Retreat
Since the 1960s, laser reflectors placed on the lunar surface have allowed scientists to measure its distance precisely. They discovered the Moon drifts away at about 3.8 centimeters annually.
Why the Moon Is Drifting Away
The Moon’s gravity pulls at Earth’s oceans, creating tidal bulges. Because Earth rotates faster than the Moon orbits, these bulges shift forward and drag on the Moon, pushing it outward.
A Brake on Earth’s Rotation
This same tidal interaction slows Earth’s spin, acting as a subtle brake. Over vast timescales, the length of a day on Earth is slowly but steadily increasing.
Days Were Once Shorter
Hundreds of millions of years ago, Earth’s days lasted just 23.5 hours. Today they are 24 hours long, a change driven by the Moon’s steady retreat and its effect on our planet’s rotation.
The Long-Term Outlook
If the process continues, days on Earth could eventually stretch to match the Moon’s orbital period—nearly 29.5 Earth days—radically altering the planet’s rhythms.
What Happens to Eclipses
As the Moon moves farther away, it will appear smaller in the sky. One day, it will no longer be able to completely cover the Sun, ending the era of total solar eclipses.
Earth and Moon in Lockstep
In the far future, Earth may become tidally locked to the Moon, always showing the same face to it—just as the Moon already always shows one face to Earth.
Measuring the Distance
The discovery relies on lunar laser ranging. Beams fired from Earth bounce off reflectors left on the surface, allowing scientists to calculate the Moon’s distance with extreme precision.
Not a Perfect Constant
The Moon’s retreat isn’t uniform. Astronomers have recorded periods of greater stability and times when the distance widened more quickly, showing the process is complex.
A Slow but Profound Change
Though barely perceptible within a human lifetime, this gradual shift has major implications for the Earth-Moon system over millions of years.
Why Scientists Keep Watching
By tracking the Moon’s slow drift, researchers gain insights into Earth’s rotation, tides, and planetary evolution—reminders that even the most familiar celestial bodies are never truly still.
This article is made and published by Asger Risom, which may have used AI in the preparation
