Q&A: Is the Moon’s Recession Evidence for a Young Earth?
From Luke in Moore, OK:
I’ve been speaking with Dr. Jay Wile about the recession of the Moon and how he believes that it creates extreme difficulties for the old-earth view (OEC). He cites the slowing of Earth’s rotation created by the tides and conservation of angular momentum as causing the Moon to recede more quickly in the past, when the earth was completely covered with water. Dr. Wile claims that if the OEC model is correct, then the Moon should be much further away than it is now. How is this young-earth challenge addressed?
Luke, thank you for your question. The tidal interaction of the Earth-Moon system transfer of angular momentum from Earth to the Moon does result in the Moon’s moving away from Earth (recession). Lunar laser ranging has established that the Moon is receding from Earth at a rate of 3.82 ± 0.07 centimeters per year.1 In 1963, physicist Louis Slichter assumed a simple model of the Earth-Moon system2 to determine that the Moon could not have receded from Earth for more than 1.4–2.3 billion years.3 Young-earth creationists cite this work and other simple-model calculations to assert that old-earth creationists must be wrong in their claims that Earth is 4.5662 billion years old and the Moon only about a hundred million years younger.
However, in his paper Slichter points out that the conflict between the measured age of Earth and his calculated lunar recession time is resolved if the tidal torque the Moon exerts on Earth was much less in the past than it is now. In 1982, physicist Kirk Hansen showed that this is indeed the case.
Hansen’s research revealed that the number, sizes, shapes, and geographical placements of the continents and their accompanying continental shelves hugely impact the Moon’s tidal torque on Earth4 and, compared to typical continental features in the past, today’s continental features generate anomalously high tidal torques from both the Moon and Sun.
Plate tectonics models and geophysical measurements confirm that roughly once every half-billion years, the planet surface undergoes the supercontinent cycle. A single supercontinent breaks up into many smaller continents, which then spread apart and later come back together to form a different single supercontinent. And a single supercontinent results in much less tidal torques than Earth’s present configuration of multiple smaller continents. Hansen concluded that the Moon was a comfortable distance from Earth 4.5 billion years ago—thus providing the resolution Slitcher mentioned.
Moreover, tidally laminated sediments (which measure the tidal torque strength) and coral reef bands (which measure Earth’s rotation rate—tidal torques operate to slow down Earth’s rotation rate) confirm that tidal torques had to be much less in the past. These observational data establish that the assumptions undergirding the simple model for the tidal interaction of the Earth-Moon system are incorrect. Therefore the recession of the Moon poses no difficulty for the old-earth view. In fact, tidally laminated sediments and coral reef bands add to the already overwhelming scientific evidence that Earth must be orders of magnitude older than what young-earth creationists declare.
- J. O. Dickey et al., “Lunar Laser Ranging: A Continuing Legacy of the Apollo Program,” Science265 (July 22, 1994): 482–90.
- No other perturbing bodies; no interference from gas, dust, or debris; no partial or total tidal-locking episodes; no change over time in the continents or the oceans; and for both Earth and the Moon, no departure from billiard ball characteristics (that is, both Earth and the Moon are presumed to be spherical, solid, and of uniform density)
- Louis B. Slichter, “Secular Effects of Tidal Friction Upon the Earth’s Rotation,” Journal of Geophysical Research 68 (July 15, 1963): 4281–88.
- Kirk S. Hansen, “Secular Effects of Oceanic Tidal Dissipation on the Moon’s Orbit and the Earth’s Rotation,” Reviews of Geophysics and Space Physics 20 (August 1982): 457–80.