Orateur
Description
Due to tidal interaction between the Earth and the Moon, dissipation occurs, slowing Earth's rotation while causing the Moon to move away from the Earth at a present rate of 3.8 cm per year. Laser reflectors left by Apollo astronauts on the Moon's surface enable extremely precise measurements of this recession. Meanwhile, rock samples brought back from the same Apollo missions helped estimate the Moon's age at 4.25 Ga. Until recently, no physical model could account for Moon's history from its formation near the Earth to its present position. This gap was filled by a scenario fitting both the age of the Moon and its measured present recession (Farhat et al., 2022). Despite agreement with geological evidence, alternate propositions arose in the recent years. One such hypothesis, a revival of ideas proposed by Zahnle and Walker (1987), suggests Earth’s spin stalled in the Precambrian due to a competition between gravitational and thermal atmospheric tides, decelerating and accelerating Earth’s spin, respectively. Thermal atmospheric tides are currently only a small fraction of the complete tidal pull on Earth, but in the past, they may have increased due to a resonance.
I will present an overview of our recent work on the Earth–Moon evolution, as well as a discussion of the ongoing controversies surrounding the possible tidal locking of Earth’s spin rate during the Precambrian.