Earth’s Days Are Getting Longer Thanks to the Moon

If you’ve ever wished there were more hours in a day, you’re in luck – sort of. Scientists have found evidence that days on Earth are gradually getting longer due to the effects of the Moon.

A new study published in the Proceedings of the National Academy of Sciences reveals that 1.4 billion years ago, a single day on our planet lasted just over 18 hours. This is partly because the Moon used to be closer to Earth, which affected how quickly our planet spun on its axis. Currently, the average distance between the Earth and the Moon is 238,855 miles (384,400 km). It is also estimated that the Moon is moving away from Earth at a rate of 3.82 centimeters per year.

“As the moon moves away, the Earth is like a spinning figure skater who slows down as they stretch their arms out,” explains Stephen Meyers, a geoscience professor at the University of Wisconsin–Madison and co-author of the study.

Meyers and his colleague Alberto Malinverno from Columbia University developed a novel technique called TimeOptMCMC. It combines astronomical theory with geological observations, called astrochronology, to reconstruct the history of the Earth-Moon system and Earth’s ancient climate patterns.

By analyzing rock layers 1.4 billion years old from Northern China and a 55 million years old record from the southern Atlantic Ocean, they could reliably determine variations in Earth’s rotation axis, orbital shape, day length, and distance from the Moon at those times.

Their findings complement other recent studies using the geological record of climate cycles to better understand Earth’s behavior over billions of years. This provides insights into the early solar system dynamics that shaped our planet’s environment.

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

While subjecting ourselves to 18-hour days may seem undesirable today, this research reveals the gradually lengthening day is a consequence of the Moon’s outward migration that has helped stabilize our climate over billions of years.

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