During its flight to Jupiter in 1992, NASA’s Galileo spacecraft returned images of the Earth and Moon. Separate images were combined to generate this view.

( NASA/JPL/USGS)

At a Glance

The moon has ever so slowly been moving away from our Earth, which has altered the planet'srotation.Currently, the moon is moving away from the Earth at a rate of 3.82 centimeters per year. A million years ago, days lasted just 18 hours.

Days on Earth lasted just 18 hours a million years ago and havebeen getting longer over the course of timethanks, in part, to the influence of the moon, researchers say.

According to a study published Mondayin the Proceedings of the National Academy of Sciences, the, which has altered the planet'srotation.

“As the moon moves away, the who slows down as they stretch their arms out,”Stephen Meyers, professor of geoscience at the University of Wisconsin-Madison and co-author of the study, said in a press release.

Using a statistical tool known as astrochronology, whichlinks astronomical theory with geological observation, the researchers were able to take a look back on Earth’s geologic past andreconstruct the history of the solar system. Through this, they were also able to have a better understanding of ancient climate change that was captured in the rock record.

“One of our ambitions was to use astrochronology to tell time in the most distant past, to develop very ancient geological time scales,” Meyers says. “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.”

The scientists note that all astronomical bodies have an influence on each other through gravitational force. This interaction also influences the Earth's place in the universe and the planet's rotational variations as it turns on its axis through millennia, known asMilankovitch cycles.

The cycles determine where sunlight is distributed on Earth, which alsodetermines Earth's climate rhythms over millions of years. These variations can be observed in the rock record going back hundreds of millions of years ago, the report notes. Going further back than that can be challenging, however, and far less reliable.

It is further complicated by solar system chaos, a theory offered by French astronomer Jacques Laskar in 1989. The theory says that tiny changes in the interactions of astronomical bodies in our solar system can lead tobig changes millions of years later.

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The scientists demonstrate this unreliability ingoing back billions of years by noting that the moon is currently moving away from the Earth at a rate of 3.82 centimeters per year.

When using this present-day rate of movement,the researchers calculatethat “beyond about 1.5 billion years ago, the moon would have been close enough that its gravitational interactions with the Earth would have ripped the moon apart,” Meyers said. Yet, that can't be possible since the moon in 4.5 billion years old.

Collaborating with Alberto Malinverno, a Lamont Research Professor at Columbia University, Meyers combineda statistical method called TimeOpt that hedeveloped in 2015 to deal with uncertainty across timewith astronomical theory, geologic data and a statistical approach called Bayesian inversionto get a better handle on our planet's uncertain past,the press release notes.

Using this new method that Meyers and Malinverno dubbed TimeOptMCMC, the scientists studied the 1.4 billion-year-old Xiamaling Formation in Northern China and a 55 million-year-old record from Walvis Ridge, in the southern Atlantic Ocean, and were able to "record variations in the direction of the axis of rotation of Earth and the shape of its orbit both in more recent time and in deep time,while also addressing uncertainty."

They were also able to determine the length of day and the distance between the Earth and the moon.

“In the future, we want to expand the work into different intervals of geologic time,” Malinverno said.