Why days on Earth are getting longer

James Marshall
June 5, 2018

According to fresh calculations, a day on Earth was a full five hours and fifteen minutes shorter a billion or so years ago, well before complex life spread around the planet.

The researchers concluded the moon was much closer to the planet in the past, exerting more spin on Earth's axis.

"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, professor of geoscience at the University of Wisconsin-Madison and co-author of the study published June 4 in the Proceedings of the National Academy of Sciences.

And the reason is because the Moon is constantly, and ever-so-slightly, moving away from us. Separate images were combined to generate this view. "We want to be able to study rocks that are billions of years old in a way that is comparable to how we study modern geologic processes".

Known as Milankovitch cycles, the researchers analyzed the changes in the orbit, tilt, and wobble of the Earth over millions of years. This uncertainty is compounded by something called solar system chaos-a theory that predicts small, early changes in the movement of the planets can eventually lead to massive variations.

But going back farther in time poses more problems.

The number means that, on average, the length of the day on Earth has grown by approximately one 74 thousandth of a second per year since Precambrian times, a trend that is expected to continue for millions, if not billions, of years more.

The moon is gradually drifting away from planet Earth in space which is making the 24 hour day just that little bit longer, the new study has astonishingly revealed.

So, Meyers sought a way to better account for just what our planetary neighbors were doing billions of years ago in order to understand the effect they had on Earth and its Milankovitch cycles. At some point in the far future, it will reach a stable distance when it will be visible only from one half of Earth, and never seen from the other. Next, they want to apply their method to other intervals of geologic time, added study co-author and Lamont Research Professor at Columbia, Alberto Malinverno in the statement.

The two geoscientists studied the relationship between Earth and the moon by analysing ancient rock sediments from 1.4 billion years ago.

The method, they discovered, could reliably evaluate Earth's rotation and orbit around the sun.

The Earth-Moon distance as reconstructed using TimeOptMCMC for the Xiamaling Formation showed that the Moon was moving away from Earth more slowly in the past - which means the amount of time our day gains per year is growing over time.

The study complements two other recent studies that rely on the rock record and Milankovitch cycles to better understand Earth's history and behavior.

Dr Meyers and his colleagues studied a rock formation in Arizona to confirm the fluctuations in Earth's orbit over a 405,000-year cycle. "They are like signposts on a trail, allowing us to navigate geological history", said Meyers.

Other reports by Click Lancashire

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