Tracing Earth-Moon History from Earth

The Apollo missions found that the moon was moving 3.8 centimeters away from Earth every year. If you go back at the current rate of the moon’s receding, you will eventually infer that the earth and the moon were together about 1.5 billion years ago. However, the moon was formed about 4.5 billion years ago, which means that the moon is currently moving away much faster than in the past. Researchers at Utrecht University in the Netherlands and the University of Geneva in Switzerland have discovered a long-term history that sheds light on the moon’s gradual “fading.” This comes not from studying the moon itself, but from reading signals in ancient rock formations on Earth. The study was published in the journal PNAS. The researchers found that the distance between the Earth and the Moon 2.46 billion years ago was about 60,000 kilometers.

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