In 1683, Sir Edmond Halley (discoverer of Halley's Comet) commenced a long series of lunar studies, discovering the Moon's secular acceleration in 1693. This was based upon Ptolemy's recordings of eclipses in Babylon in the 8th Century BC in the Almagest.
Direct measurements of the acceleration have been only been possible since 1969 using the Apollo retro-reflectors left on the Moon. The results from Lunar Laser Ranging show that the Moon's mean distance from Earth is increasing by 3.8 cm per year (Dickey, et al., 1994).
"Currently, the moon is moving away from the Earth at such a great rate, that if you extrapolate back in time -- the moon would have been so close to the Earth 1.4 billion years ago that it would have been torn apart by tidal forces (Slichter, 1963)" (McCarthy 2003).
"The implications of employing the present rate of tidal energy dissipation on a geological timescale are catastrophic. Around 1500 Ma the Moon would have been close to the Earth, with the consequence that the much larger tidal forces would have disrupted the Moon or caused the total melting of Earth's mantle and of the moon." (Williams 2000)
"This was a mystery for decades that surprised mainstream planetary scientists. It is now explained away by assuming that tidal forces were not as great during the Mesozoic as they are today." (McCarthy 2003)
However, there is no reason to believe tidal forces have changed since the Mesozoic unless Earth expansion is taking place.
Slichter, L. B., Secular Effects of Tidal friction upon the Earth's Rotation, Journal of Geophysical Research, Volume 68, Number 14, Jul 1963
Lambeck, K., The Earth's Variable Rotation: Geophysical Causes and Consequences, Page 449, 1980
Dickey, et al., Lunar Laser Ranging: A Continuing Legacy of the Apollo Program, Science, Volume 265, Number 5171, Pages 482-490, Jul 1994
Williams, G.E., Geological Constraints on the Precambrian History of the Earth's Rotation and the Moon's Orbits, Reviews of Geophysics, Volume 38, Number 1, Pages 37-59, 2000
