Looking up at the moon in the night sky, you would never imagine that it is slowly moving away from Earth. But we know otherwise. In 1969, NASA’s Apollo missions installed reflective panels on the moon. These have shown that the moon is currently moving 3.8 cm away from the Earth every year.
If we take the moon’s current rate of recession and project it back in time, we end up with a collision between the Earth and moon around 1.5 billion years ago. However, the moon was formed around 4.5 billion years ago, meaning that the current recession rate is a poor guide for the past.
