Have you ever been in the office looking at your watch and wondering why it’s taking so long for the clock to get to 5 PM? It turns out that you may be on to something.
According to a collaborative study between researchers at the University of Wisconsin-Madison and Columbia University, Earth’s days are getting longer and the moon plays a large part of the reason why.
The study discovered that around 1.4 billion years ago, an Earth day was only around 18 hours long. That’s because the moon was closer to the Earth that time and its gravitational influence caused the Earth to spin faster.
However, the moon has been steadily moving away and that’s why we’re up to 24 hours in a day now. But it doesn’t stop there because the moon is still drifting farther and that will only make the days last longer.
According to Professor Stephen Meyers, who co-authored the study, “As the moon moves away, the Earth is like a spinning figure skater who slows down as they stretch their arms out.”
In order to track the relationship between the Earth and the moon and how it has altered over time, the research team used a statistical method called astrochronology. This method correlates astronomical theory with geological observation.
This complex method allowed Professor Meyers’ team to reconstruct the history of the solar system by taking a look at Earth’s geologic past.
Professor Meyers adds, “One of our ambitions was to use astrochronology to tell time in the most distant past, to develop very ancient geological timescales.
“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.”
Because every astronomical body has some sort of gravitational force, they all exert an influence on the Earth in different degrees. Since everything is moving relative to each other, variations in a planet’s rotational axis result.
These variations are known as Milankovitch cycles. They influence factors like how sunlight falls on the Earth’s surface and can, therefore, have an impact on climate cycles.
If you try to look at these changes over the course of millions of years, the task becomes practically impossible.
However, last year Professor Meyers and his colleagues discovered a 90 million-year-old rock formation that they thought they could use to track changes in Earth’s climate cycles.
But the process wasn’t straightforward. The further back in time Professor Meyers and his team went, the less accurate their calculations were.
For instance, the moon is currently moving away from the Earth at a rate of 1.5 inches (3.82 centimeters) per year. If they used that rate to track back to the moon’s distance 1.5 billion years ago, it would have put the moon so close that the Earth’s gravitational influence would have destroyed the moon.
Yet they knew that the moon was 4.5 billion years old, so they had to be missing something. That something was provided by using results from research conducted by Professor Alberto Malinverno, Lamont Research Professor at Columbia.
The missing piece in place, the team was now able to reliably use the layers of rock to accurately measure the variations in Earth’s axis of rotation through time.
The team used 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 as a basis for their study. This is how they were able to determine the changes in the length of a day on Earth and the increasing distance between the Earth and moon.
The study first appeared in the Proceedings of the National Academy of Sciences.
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