Long before the modern 24-hour day, Earth rotated more slowly, and the length of a day changed in notable ways over deep time. Researchers from Chengdu University of Technology conducted a study that points to two distinct intervals when the planet’s rotation slowed noticeably, extending the day by roughly 2.2 hours compared with today. The findings appeared in a feature associated with the Proceedings of the National Academy of Sciences, a respected venue for peer reviewed research. The work adds a piece to the puzzle of how Earth’s early days shaped the trajectory of life on our planet, linking celestial dynamics to biological milestones.
The central claim is that the Moon’s position dictated how quickly the Earth rotated. As the Moon receded from Earth, the planet’s spin slowed. In the researchers’ model, the Moon’s recession moved the distance between the two bodies outward by a substantial amount over millions of years, explaining part of the observed deceleration in Earth’s rotation. In today’s terms the Moon sits roughly 384,400 kilometers away, but at different epochs the gap was smaller or larger as the system evolved.
The study identifies two major epochs of rapid rotational deceleration. The first spans from about 650 million to 500 million years ago. This window overlaps with a pivotal moment in biological history when the Cambrian explosion expanded the diversity of life and enabled organisms to occupy new ecological roles. The researchers argue that the longer days increased solar exposure and may have influenced environmental conditions that supported rapid biological diversification during that era.
A second slowdown occurred between approximately 340 million and 280 million years ago, a period marked by the onset of large-scale glaciations. The climate shifts associated with these ice ages would have interacted with the longer daylight hours to shape ecosystems and evolutionary pressures in new ways. Through this lens, the Moon’s outward drift is cast as a driver of orbital and climatic changes that coincide with major episodes in life’s history.
Beyond describing the timing, the study suggests a broader sequence: as day length lengthened and Earth received more prolonged sunlight, the Moon’s influence also linked to oxygenation events in the atmosphere. These oxygen surges are associated with bursts of evolutionary innovation, enabling more complex life to flourish. The authors propose that celestial mechanics and atmospheric chemistry interacted in a way that accelerated biological complexity during periods of extended daylight. The idea frames lunar dynamics not merely as an orbital curiosity but as a factor that potentially steered major steps in Earth’s biological evolution.
Earlier researchers have explored how factors such as tidal forces, ocean tides, and solar radiation can affect planetary rotation. The latest analysis adds a celestial‑climate‑biological thread to that conversation, reinforcing the view that changes in Earth’s day length are tied to profound shifts in life’s trajectory. While the exact mechanisms remain a topic of ongoing study, the narrative emphasizes a coordinated history in which lunar motion, global climate, and biological innovation move in concert over hundreds of millions of years. This perspective invites a broader understanding of how planetary dynamics may continue to influence life on Earth and, potentially, on other worlds as well.
Note: The discussion reflects interpretations reported by the Chengdu team and cited in scientific outlets. As with all long‑term astronomical and geological reconstructions, future measurements and analyses will refine the timelines and causal links among orbital dynamics, climate change, and the evolution of life.