2023 Study Says Earth’s Day Held Near 19 Hours for 1 Billion Years
Updated
Updated · spacedaily.com · May 30
2023 Study Says Earth’s Day Held Near 19 Hours for 1 Billion Years
1 articles · Updated · spacedaily.com · May 30
Summary
A 2023 Nature Geoscience paper by Ross Mitchell and Uwe Kirscher proposed that Earth’s day stayed near 19 hours from about 2 billion to 1 billion years ago.
The study says lunar tides that slow Earth’s spin were offset by solar heating-driven atmospheric tides, creating a long resonance that kept day length nearly stable until climate changes broke it.
Fossil evidence supports the broader long-term slowdown: 385-million-year-old Devonian corals record about 400 days per year, implying days of roughly 21.9 hours, while Pennsylvanian corals point to about 22.4 hours.
The underlying mechanism remains Earth-Moon tidal friction, which transfers angular momentum outward as the Moon recedes about 3.8 centimeters a year, even though short-term shifts can briefly speed Earth up.
Taken together, the findings suggest deep time had a different daily rhythm, with Earth rotating faster in the distant past before settling into today’s 24-hour day.