![]() ![]() These came from the seasonal sinusoidal growth of stromatolites (following the annual Sun angle), but such constraints require high sediment accumulation rates, which are rare in such depositional settings. When the resonance-stabilized day length hypothesis was first proposed, only a small handful of Precambrian LOD constraints were available. For Precambrian time, before the Phanerozoic, other LOD records must be used. Biologically mediated means of recording LOD, such as tree rings and coral growth bands, preserve reliable annual banding, but are restricted to the Phanerozoic eon, since 539 million years ago (Ma), when animal life evolved 9. The geological record has multiple means of preserving an archive of LOD over time and, by inference, the history of Earth–Moon distance. If the opposing atmospheric torque became equal to the diminished lunar torque, Earth’s long-term rotational deceleration could have been temporarily halted at a constant day length for some interval of Precambrian time 6. This might have been possible in the Precambrian when the lunar torque is thought to have been one-fourth of its present value due to weaker frictional coupling between Earth and the Moon at faster palaeorotation 4, 6, 7. A resonance-stabilized day length is the unique condition where, at the point of resonance, the lunar oceanic torque can be cancelled by the solar atmospheric torque. Due to the arrangement of the three-body system and Earth’s sense of rotation, the lunar semidiurnal oceanic tide applies a decelerative torque and the solar semidiurnal atmospheric tide applies an accelerative torque on Earth’s rate of rotation (Fig. In contrast with their oceanic counterpart gravitationally excited by the pull of the Moon, atmospheric tides are thermally excited by the absorption of sunlight by water vapour and ozone, the largest of which is semidiurnal. There is therefore a need for a sufficiently abundant number of Precambrian LOD constraints that can be used to further understand the evolution of the Earth–Moon system in high temporal resolution. In contrast with traditional models that propose continuously evolving conditions is the speculation of a temporarily long time interval of constant day length during Precambrian time potentially arising from a stabilization due to resonance with the atmospheric thermal tide 6, 7, 8. Theoretical lunar recession models have generally been characterized by a steady trend over the past 3 or 4 billion years 3, 4, 5. This offset exerts a torque on the Moon, which-transferring angular momentum from Earth to the Moon-boosts the Moon to a farther orbit and slows Earth’s rotation, increasing its length of day (LOD) over time. Because Earth rotates faster than the orbital angular velocity of the Moon, Earth’s oceanic tidal bulge is pushed ahead of the Moon. Tidal forces of an orbiting satellite control the evolution of a planet’s rotation 1, 2. ![]()
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