10Jun2018

Our Days Are Getting Longer Thanks To The Moon

The study was published this week in the journal 
<i>Proceedings of the National Academy of Sciences</i>.

IF YOU’RE sitting at work reading this thinking it’s been a long day, you’re closer to the truth than you realise. Because slowly but surely, our days are getting longer.

According to new research, a day on Earth 1.4 billion years ago lasted just 18 hours. Using a new statistical method called astrochronology, astronomers have peered into Earth’s deep geological past and reconstructed the planet’s history, discovering the forces at play working to change the length of our days.

Scientists at the University of Wisconsin-Madison in the US used a method that links astronomical theory with geological observation to peer further back and “tell time in the most distant past”.

They set out to create an ancient geological record of rhythmic climate changes known as Milankovitch cycles, which occur over tens of thousands of years due to periodic variations in Earth’s orbit and rotation axis.

The moon and other planetary neighbours orbiting the sun impact on the Earth’s movement. These variations ultimately determine where sunlight falls on Earth, based on the planet’s speed of rotation and tilt.

Our planet’s moon is about 4.5 billion years old and sits about 385,000 kilometres away but it used to be closer, which impacted on the way the Earth spun around its axis.

Due to tidal forces between our planet and the moon, the moon slowly spirals away from Earth at about 3.82 centimetres each year, researchers said. And that has caused Earth’s rotation to slow.

“As the moon moves away, the Earth is like a spinning figure skater who slows down as they stretch their arms out,” study co-author Dr Stephen Meyers said in a statement released by the university.

The researchers said the use of astrochronology in the research greatly improved our knowledge of early solar system dynamics. “One of our ambitions was to use astrochronology to tell time in the most distant past, to develop very ancient geological time scales,” Dr Meyers said.

“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 geological processes.” The researchers tested the approach on two stratigraphic rock layers — the 1.4-billion-year-old Xiamaling Formation from northern China and a 55-million-year-old record from Walvis Ridge, in the southern Atlantic Ocean.

Basically, the geological record acts as an astronomical observatory for the early solar system, Dr Meyers said. The technique allowed them to reliably assess from layers of rock in the geological record variations in the direction of the axis of Earth’s rotation and the shape of its orbit in deep time with an new degree of confidence. Source: News.Com

 

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