In search of a coherent scenario for the evolution of the Earth-Moon system

IAP weekly specialised seminars / 4 October 2024 Jacques Laskar (IMCCE, Observatoire de Paris, France) Since George Darwin's work in 1880, we have known that tidal interactions between the Earth and the Moon cause a slowing of the Earth's rotation and a recession of the Moon. Thanks to the laser reflectors placed on the Moon's surface by Apollo mission astronauts, we can measure this recession with very high precision at 3.83 cm per year. Lunar expeditions have also allowed us to determine the age of the Moon, set at 4.425 billion years. However, it was also realized more than fifty years ago that Darwin's tidal model leads to a collision between the Moon and the Earth about 1.5 billion years ago, which is incompatible with the age of the Moon. I will present the most recent results on this paradox, which has persisted for over fifty years. These advances stem from both new analytical modeling of the various tidal effects in the Earth-Moon system and innovative methods for deciphering geological constraints.