The Moon Is Slowly Drifting Away from Earth

The Moon is gradually moving away from Earth at a rate of about 3.8 centimeters (1.5 inches) per year. This happens because of tidal forces - the same forces that cause ocean tides. As the Moon orbits Earth, it creates tidal bulges in Earth's oceans. These bulges are slightly ahead of the Moon due to Earth's rotation, and their gravitational pull accelerates the Moon in its orbit. This extra energy causes the Moon to spiral slowly outward. As the Moon moves away, it also causes Earth's rotation to slow down due to tidal friction. This means our days are getting longer by about 1.7 milliseconds per century. When the Moon first formed about 4.5 billion years ago, it was much closer to Earth - possibly only 22,000 kilometers away compared to today's 384,400 kilometers. Back then, Earth days were only about 5-6 hours long, and the Moon appeared much larger in the sky.