The Moon will not hit the Earth. Scientific observations show our natural satellite is gradually moving away from our planet. This ongoing process is a natural consequence of gravitational interactions between the Earth and the Moon, occurring for billions of years.
The Moon’s Current Movement
The Moon is currently receding from Earth at an average rate of about 3.8 centimeters (approximately 1.5 inches) per year. This measurement is achieved using Lunar Laser Ranging (LLR) experiments. These experiments involve firing laser pulses from Earth observatories towards retroreflectors placed on the Moon’s surface by Apollo missions and Soviet Lunokhod rovers. Scientists measure the time it takes for these pulses to travel and reflect back, allowing calculation of the Earth-Moon distance with millimeter accuracy. This precise tracking confirms the Moon’s slow, outward spiral.
Forces Shaping the Lunar Orbit
The Moon’s increasing distance from Earth is driven by tidal forces. Earth’s gravity pulls on the Moon, and the Moon’s gravity pulls on Earth, causing a slight distortion or “bulge” in both the solid body of Earth and its oceans. Earth rotates faster than the Moon orbits it, pulling these tidal bulges slightly ahead of the Moon’s direct gravitational alignment.
This leading bulge exerts a gravitational tug on the Moon, continuously accelerating it in its orbit. An object gaining orbital energy moves into a higher, larger orbit. This energy transfer also gradually slows Earth’s rotation, with the length of a day increasing by approximately 1.8 milliseconds per century. This exchange of angular momentum ensures the Moon spirals outward.
The Moon’s Distant Future
The Moon’s recession will continue for billions of years. Eventually, Earth’s rotation will slow to the point where its rotation period matches the Moon’s orbital period, a state known as tidal locking. At this distant point, estimated to be about 50 billion years from now if the Sun were to remain stable, the Moon would no longer recede.
However, the ultimate fate of the Earth-Moon system will be determined by the Sun. In approximately 5 billion years, our Sun will exhaust its core hydrogen fuel and begin to expand into a red giant star. During this phase, the Sun’s outer layers will swell, potentially engulfing the inner planets, including Earth and the Moon. Even if Earth avoids direct engulfment, the intense heat and radiation from the expanded Sun would render our planet uninhabitable long before any collision with the Moon could occur.