Researchers Reconstructed Ancient Earth-Moon System
A study of billion-year-old rock layers revealed that an Earth day lasted only 19 hours in the distant past.
Updated on Sept. 25, 2026 in Geology
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Scientists analyzed 1.25 billion-year-old rock layers from the Grand Canyon to reconstruct the mechanics of the ancient Earth-Moon system. The study concluded that Earth experienced 19-hour days during that period.
Why it matters
Understanding the celestial mechanics of the ancient Earth helps researchers track the moon's gradual recession from our planet over time. This data provides a clearer picture of how Earth's rotation and orbital cycles have evolved throughout deep history.
Researchers analyzed alternating carbonate-rich and muddy layers within the Hakatai Shale to identify precession periods of 15,730 years. The study also measured the moon's distance at 53.8 Earth radii using geological patterns 65 kilometers apart.
The players
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The details
By examining the Hakatai Shale, which formed in an inland sea on the ancient continent of Laurentia, researchers traced cycles driven by Earth's rotation and orbit. The team successfully debunked theories that suggested Earth's day length had stalled at 19.5 or 21 hours during this era.
Timeline
The Hakatai Shale layers formed approximately 1.25 billion years ago.
The findings were published in Nature Geoscience in September 2026.
The Big Picture
This research applies the established framework of Milankovic cycles to recalibrate our understanding of the ancient Earth-Moon system. The findings refine existing models of planetary rotation and offer a more precise timeline for how the moon has receded from Earth over eons.
While this study focuses on billion-year-old history, the techniques used to decode cyclic patterns in rock layers help scientists better predict long-term climatic shifts. Such geological insights provide the foundational data necessary to refine our climate models for the future.
The takeaway
The study confirms that the relationship between Earth and the moon has been in a constant state of flux for over a billion years. By studying ancient rocks, scientists can effectively turn back the clock to observe the planet's changing mechanical properties.
Further reading
Learn more about local geological history in the Geology section.
Source note: This article includes information reported by ScienceAlert.
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