Most of the angular momentum of the Earth-Moon system is in the orbital motion, which is in contrast to other moons in our solar system. The orbital angular momentum of the Moon is more than 80 % of the total angular momentum.
Today, the most prevailing idea related to the origin of the Moon is the ‘Giant-Impact Hypothesis’ – a giant body should have smashed into the Earth more than 4.5 billion years ago, which is a nonsense idea for the chthonian theory based on at least two reasons:
- The hit would probably cause the water to vaporize and
- it would cause the ultracondensed matter in the interior to relax too quickly.
The Earth’s spin rates were higher at the beginning. So it is assumed that Moon has been moving away from the Earth, because of angular momentum conservation. The whole effect was caused by the slowdown of Earth’s rotation (tides).
According to chthonian theory, there were no oceans like today until 180 Ma (icy sarcophagus). This means that the spin rates were quite high 180 million years ago and the rotation slowdown was caused also by Earth’s expansion.
The most probable hypothesis for the formation of the Moon is that the Earth-Moon system was formed from the +/- same accretion disc. The Moon even has Earth-like composition. The high angular momentum of the system was made by the Earth’s initial gas giant stage.
The gas giant planets are spinning fast:
- Jupiter: 9 h 56 min
- Saturn: 10 h 42 min
- Uranus: 17 h 14 min
- Neptune: 16 h 6 min
And the universe is full of much faster spinning gas giant planets.