The eccentricity of the Moon's orbit is growing at a faster rate than can be explained using various models of the Earth and Moon interiors, possible undetected planets, General Relativity and MOND gravity. The observation of 38 mm/year is based on laser range findings of the Moon's distance since 1970. This 2011 paper surveys various explanations which all come up short. https://academic.oup.com/mnras/article/415/2/1266/1036753
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