Mid-Proterozoic day length stalled by tidal resonance

We present statistical analysis of a compilation of observational constraints on the Precambrian length of day and find that the day length stalled at about 19 h for about 1 billion years during the mid-Proterozoic. We suggest that the accelerative torque of atmospheric thermal tides from solar energy balanced the decelerative torque of lunar oceanic tides, temporarily stabilizing Earth’s rotation. This stalling coincides with a period of relatively limited biological evolution known as the boring billion. Analysis of changes in the Earth’s rotation in the Precambrian suggests that day length stabilized at 19 h for 1 billion years due to tidal resonance, which may have been linked to a relatively quiescent period of tectonic activity and biological evolution.