A new study published in the Proceedings of the National Academy of Sciences suggests the moon is moving away from Earth and causing days to lengthen by 1/75,000 of a second each year.

Researchers at the University of Wisconsin-Madison determined that 1.4 billion years ago, when the Moon was closer to us, a day on Earth lasted about 18 hours. As the Moon gets farther away, it slows down Earth’s rotation and working backward from the present day the researchers determined how long our days used to be.

“As the moon moves away, the Earth is like a spinning figure skater who slows down as they stretch their arms out,” Professor Stephen Meyers of UW-M explains.

The scientists at UW reached their findings by using a statistical method called astrochronology. The team studied two rock formations in China and the Atlantic Ocean that date back 1.4 billion and 55 million years, respectively, to better understand the ancient history of the Earth.

“The geologic record is an astronomical observatory for the early solar system,” Meyers explained. “We are looking at its pulsing rhythm, preserved in the rock and the history of life.”

According to the results, the moon has been moving 3.82cm away from Earth every single year, and that small amount is going to keep extending our days.

Meyers looked at changes in the distance between the Earth and the moon, and variations in Earth’s orbit, along with wobbles and tilts known as Milankovitch cycles, further back in time than ever before. Because Milankovitch cycles affect how much sun reaches the planet’s poles, they are prime drivers of climate change over timescales ranging from tens of thousands of years to millions of years.

“We were interested in reconstructing the Milankovitch cycles because they provide a powerful tool for evaluating the history of our planet, and the solar system. They are like signposts on a trail, allowing us to navigate geological history,” said Meyers. “For example, the identification of Milankovitch cycles in sediments spanning the past million years has revolutionized our understanding of the nature of ice ages, the instability of ice sheets, and how Earth’s climate system works.”

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